T-CELL LARGE GRANULAR LYMPHOCYTE
Table of contents :
T-LGL is a clonal disorder of cytotoxic
T lymphocytes (CTL)ref1,
The establishment of T-LGL as a leukemia rather than a reactive disorder
was based on nonrecurring chromosomal abnormalities observed in some patients
with T-LGL in conjunction with the presence of tissue infiltration in the
bone marrow, spleen, and liverref
: first described by McKenna in 1977; T-LGL represents only 4% of the chronic
however, it represents the most frequent T cell malignancyref.
Patients tend to be older, with a median age of 55; there is an equal male/female
Pediatric cases have been recognized
: central to the understanding of T-LGL leukemogenesis is the notion that
T-LGL cells are antigen activated in vivoref.
Multiple levels of evidence support this hypothesis, including immunophenotypic
data demonstrating CD45RO, HLA-DR, perforin, and CD57 expression. Functionally,
T-LGL display non-MHC–restricted cytotoxicity after anti-CD3 mAb stimulation.
Molecular evidence of common usage of TCR-ß junctional motifs suggests
antigenic pressure in the clonal evolution of the diseaseref1,
Finally, DNA microarray analysis has demonstrated upregulated proteases
while protease inhibitors are downregulated. While the source of the antigenic
activation is still uncertain, some patients with T-LGL show serum reactivity
to gag p24 and env p21e of HTLV-I
virus but do not have prototypical HTLV infection. These findings suggest
a possible infection with a retrovirus with homology to HTLV-I as an underlying
drive for the leukemic process. In contrast to normal CTL, T-LGL cells
are resistant to Fas-mediated
apoptosis. Unlike the mechanism of autoimmune lymphoproliferative disease,
no mutation in the death domain of Fas in T-LGL has been observed. Alternatively,
constitutive activation of STAT3
with upregulation of mcl-1 has been implicated in apoptotic resistance.
Furthermore, novel splice variants of soluble Fas molecules resulting in
"decoy receptors" allow T-LGL cells to circumvent immunosurveillance. A
more detailed discussion of the leukemogenesis of T-LGL is provided in
a recent reviewref.
T-LGL is frequently associated with autoimmune disorders. Rheumatoid
is the most common associated disorder, with T-LGL occurring in 25–33%
Similar to T-LGL, Felty's
is likewise characterized by neutropenia with variable splenomegaly in
conjunction with RA. Indeed it is our opinion that these disorders are
part of a single disease process. The original diagnostic criteria for
lymphoproliferative disorder of granular lymphocytes (including both T
and NK forms of LGL) required an absolute large granular lymphocytosis
in excess of 2.0 x 109/L. Since that time, patients with lower
numbers of LGLs have been shown to have similar clinical courses and response
to therapy as those meeting the former diagnostic criteriaref.
Previously published historical studies had reported a low occurrence (8%)
of LGL counts < 1.0 x 109/L, while more recent studies have
reported patients with T-LGL having LGL counts < 0.5 x 109/L
in 25%–30% of casesref1,
In such studies, the diagnosis is based on multicolor flow cytometric immunophenotyping
and molecular analysis of the TCR genes. As would be expected from this
shift, disorders originally diagnosed as FS in the past may well be classified
as T-LGL in the present. Relative frequencies of Felty’s syndrome and T-LGL
based on selected diagnostic criteria :
The number of CD3+, CD8+, CD57+ cells
is measured by flow cytometry. TCR clonal rearrangement is assessed by
Given the subtleties in diagnostic distinction, it is not surprising
that these disorders share a common immunogenetic link. Patients with FS
and T-LGL with RA have a similar frequency of the HLA-DR4 allele (80–90%)ref.
However, T-LGL patients without RA lack the elevated allele frequency and
are similar to normal racially matched controls (33%)ref.
More recently, the immunohistochemical evaluation of the T cell infiltrate
within the bone marrow of patients with T-LGL have shown the quantity and
pattern of infiltration to be specific to the diagnosisref1,
however, similar patterns of T cell infiltration have been observed in
patients with FS as those of T-LGL. What can safely be said about FS and
T-LGL with RA is that they appear to be related disorders whose distinction
is somewhat arbitrary. These disorders can be separated by the presence
of clonal TCR gene rearrangements in T-LGL, but not in FS, recognizing
that clonally expanded CD3+, CD57+ lymphocytes (LGL)
may be detected using sensitive techniques in nonneutropenic patients with
RA as well as some normal elderly individuals. What is not understood yet
is why patients with RA are especially prone to develop clonal expansions
of T-LGL. Nevertheless, it is likely that the pathogenesis of neutropenia
in these disorders overlaps. Early studies into the mechanisms of neutropenia
in FS revealed 2 distinct groups of patients :
While neutrophil autoantibody-mediated autoimmune neutropenia is perhaps
the easiest mechanism to conceptualize, it is the most difficult to evaluate
in the laboratory. Unlike red cells in autoimmune
granulocytes are more difficult to isolate and therefore a direct "Coombs
test" for neutrophils is not practical. As such, indirect assays using
patient serum and banked normal neutrophils, namely the granulocyte immunofluorescent
test (GIFT) and granulocyte agglutination test (GAT), represent the screening
methods of choice. To add further complexity, neutrophils, unlike red cells,
express HLA-antigens as well as Fc-receptors for immunoglobulin, which
limits the ability of the test to distinguish between neutrophil autoantibodies,
HLA alloantibodies, and immune complexes. The antibody-dependent lymphocyte-mediated
granulocytotoxicity test (ADLG) can detect neutrophil-bound monomeric immunoglobulin
and, with prior absorption using random pooled platelets, can distinguish
between confounding HLA alloantibodies and neutrophil autoantibodies. When
a battery of such tests is performed with FS sera, 77% have bound immunoglobulin
via either the GIFT or GAT tests. Based on the results of the ADLG test,
showing positivity on only 14%, the bound antibody appears to be made of
predominantly immune complexes. Of those with positive ADLG test, all were
inhibited by platelet absorption indicative of HLA alloantibodies, which
implies that true neutrophil autoantibodies are not presentref.
A similar analysis of 5 patients with T-LGL without RA revealed low levels
of immune complexes in only 1 patient and no definitive neutrophil autoantibodies
in the remaining 4 patientsref.
Testing for antineutrophil antibodies is not recommended for routine clinical
practice. Because of the complexity of this approach, newer techniques
have been employed to assess neutrophil-specific autoantibodies. Using
an antibody phage display library made from the RNA of FS bone marrow lymphocytes,
a putative neutrophil autoantibody was discovered. Panning against a myeloid
antigen expression library with this antibody revealed a protein identified
as eukaryotic elongation factor-1A-1 (eEF1A-1). An ELISA test, using this
factor to screen sera of patients with FS, revealed positivity in 66% of
62 patients. The antibody does not appear to be specific to FS, as positive
results were also seen in RA without neutropenia (23%) and SLE (9%), but
not normal controlsref.
Similarly, adults with atopic
without neutropenia also express antibody to eEFA1-1ref.
The frequency of eEFA1-1 autoantibodies has yet to be tested in patients
with T-LGL. Immune complexes represent another humoral mechanism by which
neutropenia may occur. Using column separation, ultracentrifugation, and
C1q binding assays, patients with FA have increased numbers of immune complexes
as compared to normal controls and patients with RA without neutropenia.
Furthermore, the neutrophil-bound immune complexes were of varying sizes
and were at least partially composed of rheumatoid factorref.
The binding of immune complexes to neutrophils leads to several important
physiologic sequelae. First, neutrophils become activated after binding
immune complexes, and the degree of activation appears to be dependent
on the type of immune complex encountered. When neutrophil activation is
measured by chemiluminescence, activation is most intense after incubation
with precipitated immune complex followed by soluble immune complex with
monomeric (non-complexed) IgG providing the least activation. Not surprisingly
then, neutrophils incubated with sera from patients with FS showed greater
activation than with sera from patients with RA and normal controlsref.
Neutrophil activation results in cellular changes that account for neutropenia.
Neutrophils incubated with sera from patients with FS, but not from patients
with RA, display increased adherence to endothelial cells in vitroref.
This mechanism of increased endothelial adherence may explain the occurrence
of transient neutropenia in mice after injection with sera from patients
with FS and to a lesser degree with sera from RA patients, while injection
of sera from normal controls results in transient elevations of the neutrophil
counts. Necropsy of mice following injection with FS sera confirmed that
the increased endothelial adherence occurs in vivo, showing increased
neutrophil margination with deposition of IgG, IgA, and IgM within vascular
These observations suggest that immune complexes may induce neutropenia
by altering the distribution of neutrophils into the marginating pool.
Finally, some types of immune complexes appear to induce neutrophil apoptosis.
The characteristics of the immune complexes appear to be critical in this
role, as precipitated immune complexes induce apoptosis while soluble immune
complexes decrease apoptosis. Neutrophils can bind immune complexes by
means of Fc-receptors, of which FcgR-II
but not FcgR-III
appears critical in the pathway of neutrophil apoptosis. Surprisingly,
CCR3 (CD11b/CD18) is not essential in precipitated immune complex-induced
apoptosis. Moreover, precipitated immune complex-induced apoptosis is independent
of the Fas/Fas-L pathway and is instead dependent upon reactive oxygen
intermediates, in particular hydrogen peroxideref.
Cell-mediated mechanisms are of critical importance in the pathogenesis
of neutropenia in T-LGL. While the mechanisms responsible for T-LGL cell
survival result from inhibition of signaling pathways leading to Fas/FasL-induced
apoptosis, the Fas/FasL system is also intimately related to neutropenia
in T-LGL. As previously discussed, T-LGL cells constitutively express Fas-ligand
(FasL) on their cell surface, whereas normal T and NK cells express FasL
only after activation. Moreover, the FasL expressed on T-LGL cells can
produce cytotoxicity against W4 cells in vitro, and this cytotoxicity
appears to be independent of the perforin pathway of cytotoxicityref.
The FasL receptor, Fas (CD95), is expressed ubiquitously on a variety of
cells including normal granulocytes. Neutrophils express higher levels
of Fas than eosinophils or monocytes. It therefore follows that neutrophils
are more susceptible to Fas-mediated apoptosis than eosinophils or monocytes
when treated with Fas-activating antibody (CH-11)ref.
Others have noted that proinflammatory cytokines such as FasL and INF-
may inhibit myeloid progenitors in patients with idiopathic chronic neutropeniaref.
While FasL is constitutively expressed on the surface of T-LGL cells, MMPs
can cleave this protein and generate soluble FasL (sFasL). In support of
this process is marked elevation of sFasL in the sera of patients with
T-LGL, NK-LGL, and NK-lymphomas but not other leukemiasref.
Indeed, sera from patients with T-LGL with elevated sFasL induce neutrophil
apoptosis in vitro in a similar fashion to Fas-activating antibody (CH-11).
Furthermore, clinical response to therapy in patients with T-LGL is associated
with a decrease in serum sFasLref.
It remains unclear, however, what significance sFasL plays in the mechanism
of neutropenia in vivo as disorders such as NK-LGL and NK-lymphomas
also exhibit high levels of sFasL but are characterized by severe pancytopenia
and hepatic dysfunction rather than the isolated neutropenia observed in
T-LGL. Furthermore, mice injected with high levels of sFasL experience
hepatic necrosis, which is uncharacteristic of T-LGLref.
As such, the pattern of neoplastic cell infiltrate better correlates with
the distribution of tissue dysfunction in these disorders, suggesting bound
FasL and perhaps the local paracrine effects of sFasL contribute to neutropenia
in T-LGL and FS, while the diluted serum sFasL represents a useful test
in monitoring disease activity. In summary, the mechanisms of neutropenia
can be attributed to problems with production, distribution, and destruction.
Unlike many of the congenital neutropenias described elsewhere in this
section, neutrophil production defects are not typical in T-LGL/FS. Examination
of the bone marrow myeloid elements in patients with T-LGL usually reveals
mild hypercellularity with left-shifted myeloid maturationref1,
This assessment would suggest that neutropenia is at least in part a result
of peripheral destruction. However, bone marrow coculture experiments with
the lymphocytes from some patients with FS results in diminished granulocyte
It appears likely then that both peripheral and intramedullary destruction
of neutrophils are responsible for neutropenia in T-LGL. Neutrophil destruction
may occur by means of immune complex induction via FcgR-II
activation leading to death by reactive oxygen intermediates. Fas-mediated
apoptosis resulting from direct contact of T-LGL cells expressing FasL
or local paracrine effects of sFasL released by the functions of MMPs also
are important in pathogenesis of neutropenia. Finally, measured neutropenia
may result from increased margination as a result of precipitated immune
complex activation of neutrophils. While these studies have approached
the mechanisms of neutropenia in T-LGL and FS independently, it should
be clear that the variability in diagnostic criteria utilized renders these
distinctions meaningless. Furthermore, it is likely that any or all the
above mechanisms are involved in the pathogenesis of neutropenia in a given
patient with T-LGL. In patients with active rheumatologic disease, immune
complexes may play a dominant role in inducing neutrophil margination and
apoptosis via reactive oxygen intermediates. In such patients, only small
populations of clonal cytotoxic T cells may exist and their contribution
to neutropenia may be less pronounced. Alternatively, patients with marked
expansions of clonal FasL-bearing T-LGL cells may experience neutropenia
as a result of Fas-mediated apoptosis in the absence of active rheumatological
disease. Still, patients with relatively inactive RA with only moderate
numbers of clonal T-LGL cells may experience severe neutropenia, and the
mechanism of this cytopenia is probably a result of the combined mechanisms
described herein. The mechanism of adult onset cyclic neutropenia in T-LGL
one group exhibited evidence of humoral mediated destruction (60%)ref.
These patients had either monomeric (non-complexed) immunoglobulin, presumed
to be neutrophil autoantibodies and/or immune complexes of varying sizesref
alternatively, about 40% of patients lacked neutrophil-bound immunoglobulin
and were reported to have depressed granulocyte colony growth in bone marrow
co-culture experiments using patient lymphocytesref.
Mechanisms of cytopenia are not clearly defined. Inhibition of erythropoiesis
in patients with pure red cell aplasia appears to be mediated directly
by leukemic LGL. In one patient with LGL of phenotype, it was demonstrated
that leukemic LGL expressing killer receptors were cytotoxic for red cell
progenitors lacking HLA class Iref.
As there may be clinical overlap with LGL leukemia, MDS, and aplastic anemia,
it is conceivable that hematologic suppression in these diseases occurs
through a similar pathway involving activated CD8+ T cells producing
inhibitors belonging to the TNF family. For example, Fas ligand plays a
role in mediating neutropenia in LGL leukemia (Liu JH, Wei S, Lamy T, et
al. Chronic neutropenia mediated by Fas ligand. Blood. 2000;95:3119–3222).
Autoimmune features are prominent in LGL leukemia. Frequent serologic abnormalities
include positive tests for rheumatoid factor and/or ANA, high levels of
circulating immune complexes, polyclonal hypergammaglobulinemia, and high
levels of ß2-microglobulinref.
Autoimmune diseases are also a characteristic finding in LGL leukemia.
Clinical, immunologic, molecular, and genetic data indicate that patients
with LGL leukemia and rheumatoid arthritis (RA) and patients with Felty's
syndrome are part of the spectrum of the same disorder. Up to one third
of neutropenic patients with RA have clonal LGL expansionsref1,
In addition, oligoclonal CD3+8+57+ T cells
have been demonstrated in RA patients (Hingorani R, Monteiro J, Pergolizzi
R, Furie R, Chartsah E, Gergersen PK. CDR3 length restriction of T-cell
receptor ß chains in CD8+ T-cells of rheumatoid arthritis patients.
American New York Of Academic Sciences. 1995;756:179–182). Increased numbers
of cells with a phenotype similar to leukemic LGL have been observed in
blood or synovial fluid of RA patientsref.
The identical MHC locus association with HLA-DRß *0401 is found in
patients with LGL/RA as well as those with Felty's syndromeref.
It has been recently recognized that clonal expansion of CD28-
T cells with many phenotypical and functional characteristics of LGL, including
CD57 and perforin expression as well as TcR-mediated cytotoxicity, is a
characteristic finding in RAref.
These data suggest a common pathogenetic link between LGL leukemia and
RA. Distinctive pathologic findings in LGL leukemia are found in bone marrow,
spleen, and liver (Agnarsson BA, Loughran TP, Jr, Starkebaum G, Kadin ME.
The pathology of large granular lymphocyte leukemia. Hum. Pathol. 1989;20:643–651).
Unlike other T cell malignancies, skin and lymph node involvement is uncommon.
It is important to emphasize that it is difficult to recognize LGL in tissue
sections; consequently morphologic findings may be indistinguishable from
other indolent lymphoproliferative disorders. Correlation with immunophenotyping
studies are therefore very helpful for diagnostic evaluation. In contrast
to our initial description of frequent lymphoid aggregates in marrow sections,
an interstitial diffuse infiltration appears more common. This finding
is particularly highlighted by use of immunostaining for T cells in marrow
sections. Typical findings in the spleen include red pulp infiltration
by leukemic cells and often reactive follicular hyperplasia of the white
pulp. This pattern of red pulp infiltration needs to be distinguished from
hairy cell leukemia, in which red pulp infiltration is especially characteristic.
Liver biopsies from LGL leukemia patients show prominent intrasinusoidal
infiltration. In cases where infiltration is marked, portal areas are sometimes
signs : infection and fever
are the presenting features in 20–40% of patients. As the infection is
related to neutropenia, common locations of infection are the skin, oropharynx,
and perirectal regions. B symptoms (fever, night sweats, and weight loss)
occur in 20–30% of patients, while about 1/3 are asymptomatic. Organomegaly
involving the spleen (20–50%) and liver (10–20%) is typical, while lymphadenopathy
and skin involvement are uncharacteristic.
leukocytosis (10,000-50,000/ml); LGL > 2,000/ml
for > 6 months
severe chronic neutropenia
(most commonly 1,000-2,000/ml)
mild to moderate anemiais
not an infrequent finding
less commonly, adult onset cyclic neutropenia, pure red cell aplasia, and
immune-mediated thrombocytopenia may be the presenting hematologic feature.
bone marrow findings demonstrate increased numbers of CTLs (lymphocytosis
20-60%) in an interstitial and sinusoidal distributionref1,
immunophenotype of peripheral blood : CD3+ (differential diagnosis
: rarely CD8-ref;
association with auto-immune diseases especially rheumatoid arthritis,
ulcerative colitis and autoimmune hepatitisref.
Clinical outcome was favorable for these patients with overall survival
of 85% at 3 years. 50% of patients required treatment and the response
to therapy was estimated at 55%. Cases of spontaneous remission have been
clonal TCR gene rearrangement at peripheral blood PCR : circulating, clonal
CD3+ LGL counts > 3 standard deviations above the number of
T cells coexpressing CD3 and CD57, an LGL marker (the normal values for
CD3+, CD57+ cells are 22 ± 99/µlref,
so some consider values above approximately 520/µl as being abnormal).
Clonality is best determined by utilization of TcR gene rearrangement studies,
either using Southern blotting or PCR. It has been recognized that patients
may have a clonal T cell population with even normal LGL counts, and such
cases would be compatible with the diagnosis of LGL leukemiaref.
Since the total lymphocyte count may not be elevated, it is recommended
that the peripheral blood smear be carefully evaluated for LGL in patients
with hematologic and/or autoimmune abnormalities suggestive of LGL leukemia.
Leukemic LGL represent antigen-driven cytotoxic T lymphocytes (CTL). Data
supporting this contention include :
hairy cell leukemia
B-cell chronic lymphocytic
follicular lymphoma (FL)
|cytology (peripheral blood)
||atypical lymphocytes and LGL
||sinus and portal infiltrates
||sinus and portal infiltrates
||sinus and portal infiltrates
||portal infiltrates infiltrates; hepatocyte injury
||sinus and portal
||red pulp infiltrate plasmacytosis
follicular hyperplasia of white pulp
|red pulp infiltrate
red cell "lakes" reduction of white pulp
|primary expansion of white pulp
frequent infiltration of red pulp
|white pulp infiltrate
||red pulp infiltrate (immunoblasts, neutrophils)
||diffuse or nodular pattern usually nonparatra- becular often subtle
involvement maturation arrest
||diffuse pattern frequent "dry tap"
||diffuse or nodular pattern
|usually nodular pattern
||usually diffuse pattern plasmacytosis paratrabecular
Perhaps the most compelling data come from analyses of molecules involved
in the cytotoxic process, perforin and Fas ligand. These proteins are only
expressed in CTL after activation. Leukemic LGL constitutively express
high levels of both perforin and Fas ligandref1,
High expression of other cytotoxic molecules, such as granzyme and calpain,
was found in leukemic LGL compared to normal CD8+ cells, using
microarray analyses. Constitutive expression of such proteins suggests
that leukemic LGL are constantly exposed to some antigen in vivo.
Although these data suggest that leukemic LGL are antigen driven CTL, the
antigen specificity of these leukemic clones is not known. It is interesting
to note that increased numbers of LGL can be seen after infection with
viruses such as CMV and HIVref
(Zambello R, Trentin L, Agostini C, et al. Persistent polyclonal lymphocytosis
in human immunodeficiency virus-1-infected patients. Blood. 1993;11:3015–3021).
CTL responding to these infections have been characterized as memory or
effector CD8+ populations based on expression pattern of antigens such
as CD28, CD45, CD62L, and perforin. Using Vß antibodies to identify
the leukemic clone, we have determined that leukemic LGL are CD3+8+57+45RA+45RO-25-62L-,
and CD28-. These data show that leukemic LGL are effector CTL.
Others have detected the clonal abnormality in both memory and effector
This effector cytotoxic phenotype of the leukemic clone is similar to that
of CTL generated after HIV infectionref.
Retroviral infection is also characterized by production of pro-inflammatory
chemokines such as RANTES, MIP1-a, and MIP1-ßref.
A similar pattern of chemokine expression is observed in patients with
LGL leukemia (unpublished observations). Taken together, these findings
suggest that retroviral infection may be a stimulus for LGL activation.
LGL leukemia patients are HIV negative; a few patients have been infected
with HTLV-I or HTLV-IIref1,
Although most patients are not infected with prototypical HTLV, sera from
these patients do show reactivity against gag p24 and env p21e of HTLV-Iref.
Epitope mapping studies have shown that reactivity against env p21e is
directed at the BA21 epitope of HTLV-Iref.
We hypothesize that a cellular or retroviral protein having homology to
BA21 may be important in the pathogenesis of LGL leukemia. Dysregulated
apoptosis is a characteristic feature of LGL leukemia. Normal CTL recognizing
viral peptide in the correct MHC context upregulate Fas ligand. Virally
infected target cells expressing Fas are then eliminated through apoptosis.
Deletion of such antigen-activated T cells occur through the same process
of Fas-mediated apoptosisref1,
Leukemic LGL express high levels of both Fas and Fas ligand (Lamy T, Liu
JH, Landowski T, et al. Dysregulation of CD95/CD95 Ligand-apoptotic pathway
in CD3+ LGL leukemia. Blood. 1998;12:4771–4777). Ilness in LGL leukemia
such as neutropenia, anemia, or RA may be caused in part by constitutive
production of Fas ligand. Accumulation of the leukemic clone is due to
inhibition of the Fas apoptotic pathway in the leukemic LGL. The mechanism
causing neutropenia in LGL leukemia has not been defined. Normal neutrophils
undergo apoptosis through Fas triggeringref.
High levels of circulating Fas ligand were found in sera from 39 of 44
patients with LGL leukemia. Serum from patients caused apoptosis of normal
neutrophils that depended partly on the Fas pathway. Resolution of neutropenia
was associated with disappearance or marked reduction in Fas ligand levels
in 10 of 11 treated patients (Liu JH, Wei S, Lamy T, et al. Chronic neutropenia
mediated by Fas ligand. Blood. 2000;95:3119–3222). These data suggest that
neutropenia in LGL leukemia is mediated by Fas ligand. Decreased levels
of Fas ligand have also been observed in a few LGL leukemia patients who
had correction of anemia on therapy (Liu JH, Wei S, Lamy T, et al. Chronic
neutropenia mediated by Fas ligand. Blood. 2000;95:3119–3222; Saitoh T,
Karasawa M, Sakuraya M, et al. Improvement of extrathymic T cell type of
large granular lymphocyte (LGL) leukemia by cyclosporin A: the serum level
of Fas ligand is a marker of LGL leukemia activity. Eur J Haematol. 200;65:272-275).
Leukemic LGL are resistant to Fas-mediated death in vitro, despite
expressing high levels of both Fas and Fas ligand (Lamy T, Liu JH, Landowski
T, et al. Dysregulation of CD95/CD95 Ligand-apoptotic pathway in CD3+ LGL
leukemia. Blood. 1998;12:4771–4777). Fas resistance can not be explained
on the basis of Fas mutationsref,
unlike children with autoimmune lymphoproliferative syndromeref.
Resistance to Fas mediated death can be overcome in vitro (Lamy
T, Liu JH, Landowski T, et al. Dysregulation of CD95/CD95 Ligand-apoptotic
pathway in CD3+ LGL leukemia. Blood. 1998;12:4771–4777)ref.
These data suggest that resistance is due to inhibition of Fas signaling
pathway in leukemic LGL. Leukemic LGL displayed high levels of activated
STAT3. Inhibition of STAT signaling with either AG-490, a JAK-selective
tyrosine kinase inhibitor, or STAT3 antisense reversed apoptotic resistance
in leukemic LGL. AG-490-induced apoptosis was independent of Bcl-XL or
Bcl-2 expression. In contrast, levels of Mcl-1 expression decreased in
leukemic LGL after AG-490 treatment and that Mcl-1 is a STAT-3 regulated
gene. STAT3 activation contributes to the accumulation of the leukemic
LGL clones, possibly through upregulation of the anti-apoptotic protein
These results identify the STAT3 signaling pathway as molecular targets
for drug discovery in LGL leukemia
the unique subset of normal CD3+ LGL may represent in vivo
CTL directed against viral targetsref
the CD3+8+57+DR+ phenotype
of leukemic LGL and the rapid triggering of non-MHC-restricted killing
via CD3/CD16 pathwayref1,
structural analysis of rearranged TCR genes as well as TCR Vß repertoire
analyses in some LGL cases have provided evidence for antigenic selectionref1,
Therapy : T-LGL
is an indolent disorder that responds well to immunosuppressive therapies.
Indications for therapy of T-LGL include severe neutropenia
< 500/mL or recurrent infections due to chronic, less severe neutropenia.
Symptomatic or transfusion-dependent
anemia are other reasons for initiating treatmentref.
The majority of patients with T-LGL (75%) will require therapy over the
course of their disease, although rare cases will spontaneously remit.
10 mg/m2/week orally induces complete remission in 50% of patients;
however, it is likely that indefinite treatment is required to prevent
relapse. It is important to note that several months of therapy are generally
required before counts improve. Cyclosporine
represents an alternative therapy to methotrexate. In a study of 25 patients,
50% had response to therapy, with 24% gaining complete remission. It is
interesting to note that therapeutic response to cyclosporine A is related
to HLA-DR4 haplotype, which is common in patients with FS and T-LGL with
In addition, patients with concurrent T-LGL and myelodysplasia
have a lower response to cyclosporine A than patients with T-LGL aloneref.
has been used orally to treat T-LGL with good responseref.
in combination with cyclophosphamide appears to increase the duration of
response compared to prednisone alone. Overall response to therapy with
prednisone and cyclophosphamide is 66% with a median duration of 32 months.
2 prospective therapeutic trials are currently underway. The Eastern Cooperative
Oncology Group (ECOG) is evaluating the efficacy of oral methotrexate 10
mg/m2/week with crossover to cyclophosphamide in non-responders.
The Cancer and Leukemia Group B (CALGB) is testing cyclosporine A orally
2 mg/kg/q12 hours as front-line therapy. Indications for both trials are
neutropenia or symptomatic or transfusion-dependent anemia. Because immunosuppressive
therapies slowly correct neutropenia, hematopoietic growth factors such
may induce more rapid correction of the neutrophil count in patients with
Active agents for treatment of this disease are drugs which are
categorized as immunosuppressants and include oral low-dose methotrexate
(10 mg/m2 po once weekly), cyclosporine (2 mg/kg po q12 hours),
oral cyclophosphamide (100 mg po daily), and prednisone (1 mg/kg po daily)ref1,
Prednisone alone is not recommended as cytopenias almost always recur as
the dose of prednisone is taperedref.
Low dose methotrexate has been used by us primarily for treatment of severe
neutropenia. In a small series we documented a complete remission in 50%
This favorable response was also observed in a group of patients who had
both LGL leukemia and rheumatoid arthritisref.
Cyclosporine has also been used effectively for correcting neutropenia
in some patientsref.
LGL leukemia was identified as the most common cause of pure red cell aplasia
in two large single institution studiesref1,
Immunosuppressive therapy typically given to patients with pure red cell
aplasia was effective in the cases associated with LGL leukemiaref.
A small proportion of patients with LGL leukemia will present with a more
aggressive clinical courseref1,
In such cases, lymphoma type regimens do not appear particularly effective
although reported experience is quite limitedref1,
This resistance might be explained on the basis of leukemic LGL expressing
high levels of multidrug resistant genes such as P-glycoprotein and lung
Some of these patients failing combination chemotherapy have had sustained
clinical responses to low dose methotrexate and prednisoneref.
The mechanisms of therapeutic response in LGL leukemia are not well understood.
Retrospective analyses of patients treated primarily with methotrexate
did show that responses were associated with decreased levels of Fas ligand.
It is likely that a similar mechanism occurs in patients treated with cyclosporine,
as resolution of neutropenia occurs despite persistence of the leukemic
Indeed reduction of Fas ligand levels on cyclosporine treatment have been
observed in a case report (Saitoh T, Karasawa M, Sakuraya M, et al. Improvement
of extrathymic T cell type of large granular lymphocyte (LGL) leukemia
by cyclosporin A: the serum level of Fas ligand is a marker of LGL leukemia
activity. Eur J Haematol. 200;65:272-275). It is likely that methotrexate
has additional mechanisms of action. Prolonged methotrexate therapy of
1-2 years duration does result in complete remission and disappearance
of the leukemic clone in some patients, in contrast to cyclosporine therapyref.
Methotrexate treatment leads to reversal of apoptotic resistance seen in
leukemic LGL. Preliminary studies from our lab indicate that methotrexate
induces apoptosis of activated T cells through a mitochondrial-dependent
pathway. We are currently investigating whether regulation of Mcl-1 is
involved in the mitochondrial pathway triggered by methotrexate.
Clinical trials : enrollment into clinical trials should be encouraged
as there are only limited treatment data available, as noted above. 2 trials
are currently being conducted in the cooperative group setting. Both of
these trials involve correlative laboratory studies designed to examine
mechanisms of treatment response. ECOG is studying initial treatment of
LGL leukemia with methotrexate (TP Loughran, PI) whereas CALGB is investigating
cyclosporine (Maria Baer, PI, Roswell Park). Indications for treatment
in both studies include either neutropenia (ANC < 500 or neutropenia
with recurrent infections) or anemia (ECOG: symptomatic or transfusion-dependent
anemia: CALGB: hemoglobin < 9g/dL). A national registry for LGL leukemia
is established at Moffitt
Cancer Center in order to define the natural history and prognosis
of this disease.
Prognosis : in
the largest series of 68 patients reported from a single institution, the
median survival was superior to 10 yearsref.
In an earlier smaller series we had reported that actuarial survival at
5 years was 67% (Loughran TP Jr. Clinical course of LGL leukemia. Fundamental
and Clinical Immunology. 1994;2:147–151). However, the majority of patients
in both series eventually needed treatment for symptoms resulting from
neutropenia or anemia (69% and 89%, respectively). Onlu 2-3% have an aggressive
: LGL Registry
Dr Loughran maintains at Penn State Hershey Cancer Institute in the USA
Dr. T Lamy maintains one in Europe.
Copyright © 2001-2014 . All rights reserved | | |
| | |
| | |