Recombination pattern of the TCR γ locus in human peripheral T-cell lymphomas

The recombination events of the γ and β T-cell receptor (TCR) loci were analysed in a series of 39 peripheral T-cell lymphomas (PTCLs) in association with the expression of TCR chains. In TCR αβ PTCLs, 22/23 cases showed a γ-gene rearrangement while only 18/23 showed a concomitant β-gene rearrangement. The germline configuration of the β locus was found in angioimmunoblastic lymphadenopathy and lymphoepithelioid lymphomas. Three γδ PTCLs rearranged both γ and β genes. TCR silent PTCLs showed three different patterns of γ- and β-gene rearrangements. Three cases were in germline configuration for both loci; five cases had a rearranged γ and a germline β locus; and five cases had the two loci rearranged. Regarding the variable genes in the γ-rearranged alleles, members of the VγI subgroup were the most frequently presented (39/50), followed by VγII, VγIII, and VγIV (9/50, 1/50, and 1/50, respectively). Joining segment usage was as follows: J1 or J2 (32/50), JP1 or JP2 (17/50), and JP (1/50). Taken together, these data demonstrate that the γ locus is more frequently rearranged whatever the TCR expression. The γ-locus analysis provides a better diagnostic yield than the β locus in the study of PTCL clonality.     

Expression of cytotoxic molecules in intestinal T-cell lymphomas

Intestinal T-cell lymphoma (ITCL) represents a subgroup of peripheral T-cell lymphomas which is thought to arise from αβ intraepithelial T-lymphocytes. Since these lymphocytes may contain cytotoxic molecules, the question of whether this also holds true for ITCL arises. Twenty ITCL cases were examined for the presence of granzyme B, perforin, and T-cell-restricted intracellular antigen (TIA-1)/granule membrane protein of 17 kD (GMP-17). Two molecules with restricted expression in cytotoxic cells, granzyme B and perforin, were detected by immunocytochemistry and by in situ hybridization with an isotopically labelled RNA probe, respectively. Immunocytochemistry was also performed with the antibody 2G9, which recognizes two molecules, one expressed by cytotoxic cells (TIA-1) and the other found in granulocytes and cytotoxic cells (GMP-17). Granzyme B, TIA-1/GMP-17, and perforin were found in the neoplastic cells of 16/19 cases, 19/20 cases, and 16/17 cases, respectively, of ITCL, but not in the tumour cells of the control group, which consisted of intestinal B-cell lymphomas (five cases) and CD8-negative peripheral nodal T-cell lymphomas (six cases). At least one of these molecules was expressed in the tumour cells of all ITCL cases. 2G9 proved to be the most sensitive immunohistological marker, since reactivity with this antibody was not only observed in the highest number of cases, but also found in high numbers of neoplastic cells in positive cases. In conclusion, ITCL appears to show cytotoxic differentiation in all cases. In conjunction with immunophenotypic and genotypic data, our results support a uniform derivation of this tumour from intraepithelial αβ cytotoxic T-lymphocytes. © 1997 John Wiley & Sons, Ltd.     

Hepatosplenic gammadelta T-cell lymphoma: relation to Epstein-Barr virus and activated cytotoxic molecules

AIMS: Hepatosplenic gammadelta T-cell lymphoma (TCL) is a rare, aggressive subset of peripheral TCL that presents with hepatosplenomegaly and cytopenia. Epstein-Barr virus (EBV) infection and activated cytotoxic molecules (granzyme and perforin) are uncommon in hepatosplenic gammadelta CTL. EBV infection and activated cytotoxic molecules are occasionally detected in non-hepatosplenic gammadelta TCL. We describe the clinicopathological features of three Japanese cases who were not immunodeficient. METHODS AND RESULTS: All cases showed gammadelta T-cell type (CD2+, CD3+, T-cell receptor (TCR)delta-1+, betaF1-). Two cases expressed natural killer (NK) cell-associated antigens (CD8-, CD16+, CD56+; CD8-, CD16-, CD56+), and one expressed CD8 (CD8+, CD16-, CD56-). All cases expressed cytotoxicity-associated molecules (perforin, granzyme B, TIA-1 and Fas ligand). However, perforin and Fas ligand were not detected in one case. In-situ hybridization analysis with EBER probes revealed strong nuclear positivity in all neoplastic cells. In addition, two cases showed clonal bands of the EBV terminal repeat (TR) gene. Cytologically, instead of the presence of monomorphic medium-sized cells, our three cases showed pleomorphic medium-sized and large cells. CONCLUSIONS: Our gammadelta TCL cases were clinicopathologically considered to be compatible with hepatosplenic gammadelta T-cell lymphoma. However, with regard to EBV association, activated cytotoxic profile and cytological features they resembled non-hepatosplenic gammadelta TCL. EBV may play a role in this disease by inducing cellular activation.     

T cell receptor α gene rearrangement and transcription in adult thymic γδ cells

T cells belong to two separate lineages based on surface expression of αβ or γδ T cell receptors (TCR). Since during thymus development TCR β, γ, and δ genes rearrange before α genes, and γδ cells appear earlier than αβ cells, it has been assumed that αδ cells are devoid of TCR α rearrangements. We show here that this is not the case, since mature adult, but not fetal, thymic γδ cells undergo VJα rearrangements more frequently than immature αβ lineage thymic precursors. Sequence analysis shows VJα rearrangements in γδ cells to be mostly (70 %) nonproductive. Furthermore, VJα rearrangements in γδ cells are transcribed normally and, as shown by analysis of TCR β-/- mice, occur independently of productive VDJβ rearrangements. These data are interpreted in the context of a model in which precursors of αβ and γδ cells differ in their ability to express a functional pre-TCR complex.     

TIA-1 expression in lymphoid neoplasms. Identification of subsets with cytotoxic T lymphocyte or natural killer cell differentiation.

TIA-I is a 15-kd cytotoxic granule-associated protein expressed in natural killer (NK) cells and cytotoxic T lymphocytes. TIA-1 expression was evaluated by paraffin immunohistochemistry in 115 T- or NK-cell neoplasms, 45 B-cell neoplasms, and 45 Hodgkin''s lymphomas. TIA-1-positive granules were identified within the cytoplasm of neoplastic cells in 6/6 large granular lymphocytic leukemias, 11/11 hepatosplenic T-cell lymphomas, 15/15 intestinal T-cell lymphomas, 6/6 NK-like T-cell lymphomas of no special type, 2/2 NK-cell lymphomas, 8/9 nasal T/NK-cell lymphomas, 7/8 subcutaneous T-cell lymphomas, 4/5 pulmonary T- or NK-cell angiocentric lymphomas (lymphomatoid granulomatosis), 12/19 T-cell anaplastic large-cell lymphomas, 2/12 nodal peripheral T-cell lymphomas, 1/3 CD8+ cutaneous T-cell lymphomas, and 5/38 classical Hodgkin''s disease. All B-cell neoplasms, nodular lymphocyte-predominant Hodgkin''s disease (7 cases), CD4+ cutaneous T-cell lymphomas (6 cases), adult T-cell leukemia/lymphomas (3 cases), T-cell chronic or prolymphocytic leukemias (3 cases), and T-cell lymphoblastic leukemia/lymphomas (7-cases) were TIA-1 negative. These findings indicate that most large granular lymphocytic leukemias, hepatosplenic T-cell lymphomas, intestinal T-cell lymphomas, NK-like T-cell lymphomas, NK-cell lymphomas, nasal T/NK-cell lymphomas, subcutaneous T-cell lymphomas, pulmonary angiocentric lymphomas of T or NK phenotype, and anaplastic large-cell lymphomas are cytotoxic T-or NK-cell neoplasms.     

Nodal T/NK-cell lymphoma of nasal type: a clinicopathological study of six cases

Aims:  To investigate the clinicopathological features of six unusual cases of nodal CD56+ and Epstein–Barr virus (EBV)+ T/natural killer (NK)-cell lymphoma, a putative nodal counterpart of nasal NK/T-cell lymphoma (nodal T/NK-cell lymphoma of nasal type) in comparison with nasal NK/T-cell lymphoma with secondary lymph node involvement ( n  = 24) and peripheral T-cell lymphoma (PTCL) of cytotoxic molecule (CTM)+ and EBV+ type ( n  = 21).
Methods and results:  All cases of nodal T/NK-cell lymphoma of nasal type exhibited diffuse infiltration of pleomorphic medium-sized to large tumour cells, reminiscent of those in CTM+ EBV+ PTCL. The tumour cells had a typical phenotype of nasal NK/T-cell lymphoma: CD2+, CD3ε+, CD4−, CD5−, CD56+, T-cell intracellular antigen-1+, granzyme B+, perforin+ and EBV+. However, four of six cases demonstrated clonal T-cell receptor γ-gene rearrangement on polymerase chain reaction analysis, unlike nasal NK/T-cell lymphoma. Comparison of clinical parameters and overall survival among the three groups demonstrated only minor differences.
Conclusions:  Nodal T/NK-cell lymphoma may occupy the grey zone between extranodal nasal-type NK/T-cell lymphoma and nodal CTM+ PTCL in a spectrum of NK to T-cell lymphomas that are EBV+. The close relationship between NK/T-cell lymphomas and cytotoxic T-cell lymphomas was also substantiated.     

In situ detection of activated cytotoxic cells in follicular lymphomas.

The presence of cytotoxic cells and their activation status were analyzed in tissue sections of 26 follicular lymphomas. To this end, expression of the perforin and granzyme B genes was studied by in situ hybridization experiments, and expression of the TIA-1 antigen was analyzed by immunohistochemistry. Cells expressing the granzyme B gene and the perforin gene were detected in all cases. Their density was, however, highly heterogeneous from case to case, ranging from 160 to 7,040 positive cells/cm2 of tissue sections. TIA-1-positive cells were also evidenced in the 10 follicular lymphomas tested. Virtually all cytotoxic cells were located in interfollicular areas. Double labeling immunochemical experiments showed that most cytotoxic cells belonged to the CD8+ T lymphocyte population, although few CD4+ T lymphocytes and CD56+ natural killer cells also expressed the TIA-1 antigen. These findings show that development of a malignant B lymphocyte proliferation is associated with a host-derived immune response involving intratumoral cytotoxic T lymphocytes. Further studies comparing the density of such cells with the final outcome are required to determine whether the intensity of this immune response has a prognostic value.     

αβ Lineage-committed thymocytes can be rescued by the γδ T cell receptor (TCR) in the absence of TCR β chain

Commitment of the αβ and γδ T cell lineages within the thymus has been studied in T cell receptor (TCR)-transgenic and TCR mutant murine strains. TCRγδ-transgenic or TCRβ knockout mice, both of which are unable to generate TCRαβ-positive T cells, develop phenotypically αβ-like thymocytes in significant proportions. We provide evidence that in the absence of functional TCRβ protein, the γδTCR can promote the development of αβ-like thymocytes, which, however, do not expand significantly and do not mature into γδ T cells. These results show that commitment to the αβ lineage can be determined independently of the isotype of the TCR, and suggest that αβ versus γδ T cell lineage commitment is principally regulated by mechanisms distinct from TCR-mediated selection. To accommodate our data and those reported previously on the effect of TCRγ and δ gene rearrangements on αβ T cell development, we propose a model in which lineage commitment occurs independently of TCR gene rearrangement.     

Primary CD30-positive cutaneous T-cell lymphomas and lymphomatoid papulosis frequently express cytotoxic proteins

AIMS: To analyse the relationship between expression of cytotoxic proteins, histopathology and the CD30 status in primary cutaneous T-cell disorders, we investigated the expression of TIA-1, granzyme B and perforin in CD30 negative and CD30 positive cutaneous T-cell lymphomas (CTCL) and lymphomatoid papulosis (LP). METHODS AND RESULTS: We studied 26 cases of CTCL and 12 cases of LP for the expression of TIA-1, granzyme B and perforin which are granule-associated proteins of cytotoxic lymphocytes involved in the mechanism of apoptosis. We showed that most cases (10/13) of CD30 negative pleomorphic lymphomas expressed cytotoxic proteins only in scattered, apparently reactive lymphocytes, the exception being one CD8+ CTCL and two gammadelta subcutaneous 'panniculitis-like' T-cell lymphomas. We also showed that at least one cytotoxic protein was expressed in a proportion of neoplastic cells in 77% (10/13) of CD30+ T-cell lymphomas (3/4 pleomorphic and 7/9 anaplastic) and in a proportion of atypical cells in 75% (9/12) of LP. CONCLUSIONS: Our findings show a strong correlation between the CD30 phenotype and the expression of cytotoxic proteins in primary CTCL. In addition, these results provide further evidence for an overlap between lymphomatoid papulosis and cutaneous CD30+ pleomorphic and anaplastic lymphomas. These entities, which belong to the spectrum of CD30 positive cutaneous T-cell lymphoproliferations, appear to be derived from cytotoxic cells.     

Revising the historical collection of epithelioid cell‐rich lymphomas of the Kiel Lymph Node Registry: what is Lennert’s lymphoma nowadays?

Hartmann S, Agostinelli C, Klapper W, Korkolopoulou P, Koch K, Marafioti T, Piccaluga P P, Patsouris E, Pileri S & Hansmann M‐L
(2011) Histopathology  59 , 1173–1182
Revising the historical collection of epithelioid cell‐rich lymphomas of the Kiel Lymph Node Registry: what is Lennert’s lymphoma nowadays? Aims: Lennert’s lymphoma is a rare variant of peripheral T‐cell lymphoma (PTCL) not otherwise specified (NOS). The aim of this study was to further characterize this tumour. Methods and results: Historical material of 97 lymphomas with a high content of epithelioid cells, collected at the Kiel Lymph Node Registry were reviewed, by applying immunohistochemistry and current diagnostic criteria. Among all cases revised, various B‐cell lymphoma entities (25 cases), Hodgkin lymphomas (21 cases) and PTCL subtypes (48 cases) could be identified. A distinctive subgroup of eight PTCLs was found that were regarded as genuine Lennert’s lymphomas. These cases were characterized by mild atypia, a non‐activated cytotoxic phenotype [TIA1 cytotoxic granule‐associated RNA binding protein (TIA1)‐positive⁺ and granzyme B‐negative], and a substantial lack of follicular T‐helper (T_FH) cell markers. Among the other PTCLs, including angioimmunoblastic T‐cell lymphoma and PTCL NOS, many cases with positivity for more than three T_FH cell‐associated molecules were recorded. Conclusions: Our study shows that, according to current criteria, Lennert’s lymphoma is a rare but distinctive entity among epithelioid cell‐rich lymphomas, differing on grounds of morphology and immunophenotype from other PTCL subtypes. An additional finding is the broad morphological spectrum of epithelioid‐cell rich PTCLs showing a T_FH cell phenotype.     

Epstein-Barr virus is present in neoplastic cytotoxic T cells in extranodal, and predominantly in B cells in nodal T non-Hodgkin lymphomas

Epstein-Barr virus (EBV)-positive T non-Hodgkin lymphomas (T-NHLs) have been described, but it is at present unknown how EBV infects T lymphocytes. It has been postulated that cytotoxic T cells (CTLs) or natural killer (NK) cells can be infected by EBV during the killing of an EBV-infected target cell. The objective of this study was therefore to determine whether the neoplastic cells in EBV-positive T-NHLs (n=221) of various locations have a cytotoxic phenotype. To identify EBV-harbouring cells, combinations were used of EBV-encoded RNA (EBER) in situ hybridization (RISH) and immunohistochemistry for T- and B-cell markers and the cytotoxic proteins TIA-1 and granzyme B. EBV was detected in the neoplastic cells of all nasal T-NHLs (n=9), 5/34 gastrointestinal (GI) T-NHLs, and 2/6 lung T-NHLs, but not in primary cutaneous T-NHLs (n=103). Moreover, EBV was found in the neoplastic cells of 2/48 nodal anaplastic large cell lymphomas (ALCLs), but not in neoplastic T cells of other nodal T-NHLs. However, 5/17 nodal peripheral T-NHLs not otherwise specified (PTCLs NOS) and 1/4 T-prolymphocytic leukaemias did contain EBV-positive non-T cells. Double staining revealed that in EBV-positive extranodal T-NHLs (n=16), the EBER-positive cells had a cytotoxic phenotype (TIA-1- and/or granzyme B-positive). In nodal non-ALCL T-NHLs, the EBER-positive cells were not positive for TIA-1 or granzyme B, nor did they express CD3, CD21 or HECA452. Instead, most of these cells expressed the B-cell marker CD20. These PTCLs NOS with EBER-positive cells showed features of AILD-like T-NHL. It is concluded that neoplastic cells of EBV-positive extranodal T-NHLs always have a cytotoxic phenotype, supporting the view that EBV can infect CTLs. In nodal non-ALCL T-NHL, EBV is only found in T-NHL with AILD-like features and is present in B cells, where it may contribute to the outgrowth of a malignant B-cell clone.     

Comparative ultrastructural study of cytotoxic granules in nasal natural killer cell lymphoma, intestinal T-cell lymphoma, and anaplastic large cell lymphoma

Comparative immunohistochemical and ultrastructural studies were performed on five nasal natural killer (NK) cell lymphoma cases, two intestinal T-cell lymphoma cases, and eight anaplastic large cell lymphoma (ALCL) cases to clarify morphological differences in cytotoxic granules among these cytotoxic lymphomas. Nasal NK-cell lymphomas and intestinal T-cell lymphomas had fine azurophilic granules and displayed dot-like immunostaining of granzyme B- and T-cell intracellular antigen 1 (TIA-1), predominantly in the central area of the cytoplasm. Ultrastructurally, these NK-cell lymphomas and intestinal T-cell lymphomas had two types of cytotoxic granules, type-I granules (dense core granules) and type-II granules (multivesicular bodies), which have been demonstrated in normal large granular lymphocytes in peripheral blood. However, ALCLs did not have azurophilic granules, and only type-II cytotoxic granules were found ultrastructurally, even though they showed similar dot-like immunostained patterns of granzyme B and TIA-1, as seen in NK-cell lymphomas and intestinal T-cell lymphomas. Immunoelectron microscopy revealed that TIA-1 was primarily located at the periphery of the cytoplasmic granules in the NK-cell lymphoma and ALCL cases. These findings suggest that malignant lymphomas with a cytotoxic phenotype can be divided into two types, (azurophilic granule)+, (type-I granule)+, (type-II granule)+ lymphomas and (azurophilic granule)-, (type-I granule)-, (type-II granule)+ lymphomas.     

T cells expressing the γδ T cell receptor are not required for egg granuloma formation in schistosomiasis

Immunopathology in schistosomiasis consists of a granulomatous response around parasite eggs. It has been established that granuloma formation is mediated by CD4⁺ T helper cells. However, the role of T cells bearing the γδ T cell receptor (TCR) has not been determined. In this study we utilized mutant mice that lack either αβ or γδ T cells as a result of gene targeting to investigate the relative roles of αβ and γδ T cells in the induction of immunopathology related to schistosomiasis. Mutant and control mice were infected with Schistosoma mansoni and granuloma formation as well as lymph node cell proliferative responses to egg antigens were analyzed after 8 weeks. TCR δ mutant mice (lacking γδ T cells) displayed vigorous formation of egg granulomas that were not significantly different from those observed in normal controls, both in terms of granuloma size and cellular composition. In contrast, TCR α and TCR β mutant mice (lacking αβ T cells) were unable to form granulomas. Moreover, mesenteric lymph node cells from TCR δ mutant and control mice responded strongly to egg antigens in vitro, while TCR α and β mutant mice did not. Our studies show that in schistosomiasis granuloma formation and proliferative responses to egg antigens are strictly dependent on αβ T cells. They also suggest that γδ T cells by themselves can neither mediate a granulomatous inflammation, nor significantly modify one mediated by αβ T cells.     

Liver distribution of γδ‐T‐cells in patients with chronic hepatitis of different etiology

The γδ T cells represent a minor unique T‐cell subpopulation long been considered as innate‐like immune cells. They are found in increased numbers in tissues from various inflammatory conditions. Their role in chronic hepatitis, however, is still discussed controversially. Fresh frozen tissues from 50 patients (18 cases hepatitis B infection, 25 hepatitis C, three cases with co‐infection of hepatitis B and C and four patients with autoimmune hepatitis) were investigated. Immunohistochemistry with primary antibodies detecting αβ and γδ TCR was used to evaluate their incidence and distribution in the different histological structures of the liver. The inflammatory infiltrate in all cases of chronic hepatitis was dominated by αβ T cells and was mainly localized in the portal tracts with formation of an interface hepatitis (95.3%αβ T cells; 4.7%γδ T cells). There were neither significant differences between inflammatory infiltrate nor the amount or percentage of γδ T cells between hepatitis B, C or autoimmune hepatitis. No accumulation of γδ T cells could be observed in cases of chronic hepatitis of different etiologies. The immune‐mediated phenomena in chronic hepatitis are dominated by αβ T cells. Thus, the adapted immune system is responsible for the inflammatory processes in chronic hepatitis.     

Evidence that productive rearrangements of TCR γ genes influence the commitment of progenitor cells to differentiate into αβ or γδ T cells

Two models have been considered to account for the differentiation of γδ and αβ T cells from a common hematopoietic progenitor cell. In one model, progenitor cells commit to a lineage before T cell receptor (TCR) rearrangement occurs. In the other model, progenitor cells first undergo rearrangement of TCRγ, δ, or both genes, and cells that succeed in generating a functional receptor commit to the γδ lineage, while those that do not proceed to attempt complete β and subsequently α gene rearrangements. A prediction of the latter model is that TCRγ rearrangements present in αβ T cells will be nonproductive. We tested this hypothesis by examining Vγ2-Jγ1Cγ1 rearrangements, which are commonly found in αβ T cells. The results indicate that Vγ2-Jγ1Cγ1 rearrangements in purified αβ T cell populations are almost all nonproductive. The low frequency of productive rearrangements of Vγ2 in αβ T cells is apparently not due to a property of the rearrangement machinery, because a transgenic rearrangement substrate, in which the Vγ2 gene harbored a frame-shift mutation that prevents expression at the protein level, was often rearranged in a productive configuration in αβ T cells. The results suggest that progenitor cells which undergo productive rearrangement of their endogenous Vγ2 gene are selectively excluded from the αβ T cell lineage.     

Frequent detection of Epstein–Barr virus-infected B cells in peripheral T-cell lymphomas

Although Epstein–Barr virus (EBV) positivity has been described in peripheral T-cell lymphomas (PTCLs) in Chinese patients, the cellular lineage of EBV-harbouring cells is unknown. Forty-four cases of PTCL were therefore studied by in situhybridization (ISH) for EBV-encoded small non-polyadenylated RNA 1 and 2 (EBER), and the lineage of the EBER+ cells was determined by double labelling. The findings were further correlated with the clonality of EBV and the genotype of these EBER+ tumours. The results for the detection of EBV by ISH show that 23 of the 44 cases were EBER+. In 5/23 of the EBER+ cases, EBER was found in around 50 per cent of atypical cells and in 18/23 cases, EBER was found in a subpopulation of atypical cells. Amongst the EBER+ cases, all 15 tested showed clonal T-cell receptor gene rearrangement by Southern blot hybridization. Double labelling was successfully done in 11 EBER+ cases, and by comparison, EBER+/CD20+ B cells outnumbered the EBER+/CD3+ T cells in all these cases. EBV clonality analysis revealed that EBV was monoclonal in six EBER+ cases and biclonal in three cases. With the predominance of EBV+ B cells over EBV+ neoplastic T cells being observed in most of these cases, it is possible that the EBV-infected clonal population may be of B-cell lineage. This was supported in some cases where a faint clonal band was seen over a background smear in the gene rearrangement study of immunoglobulin heavy chain gene by polymerase chain reaction (PCR), indicating a minor B-cell clone. It is concluded that in EBV+ PTCL, EBV is preferentially localized in B cells rather than neoplastic T cells. The neoplastic T cells may support the clonal proliferation of a subpopulation of EBV+ B cells in PTCLs. © 1998 John Wiley & Sons, Ltd.     

Enteropathy-associated T-cell lymphomas have a cytotoxic T-cell phenotype

 

Aims:

Enteropathy-associated T-cell lymphoma (EATCL) is a rare complication of coeliac disease. We investigated whether EATCLs are the neoplastic counterparts of activated cytotoxic T-cells (CTLs).  

Methods and results:

Eight cases, clinically and histologically defined, were stained with monoclonal antibodies against components of the cytotoxic granules of CTLs, granzyme B and T-cell restricted intracellular antigen (TIA-1). It was found that all cases had a cytotoxic phenotype, i.e. expression of TIA-1 in most of the tumour cells, whereas granzyme B was found in six of eight cases, mostly in a smaller number of tumour cells compared to TIA-1. Since TIA-1 and granzyme B are expressed at different stages of activation of CTLs it is hypothesized that differences in expression between granzyme B and TIA-1 in EATCL represent different stages of activation in which the tumour cells are arrested. Clinically, seven of the eight patients died within 10 months after diagnosis of EATCL.  

Conclusions:

EATCL is a clinicopathological entity with a grim prognosis and with tumour cells representing a unique neoplastic equivalent of CTLs arrested in varying stages of activation.     

Significant involvement of nuclear factor‐κB‐inducing kinase in proper differentiation of αβ and γδ T cells

Nuclear factor‐κB‐inducing kinase (NIK) is known to play a critical role in maintaining proper immune function. This is exemplified in the spontaneous mutant mouse lacking functional NIK, alymphoplasia (aly), which is simultaneously immune‐compromised and autoimmune‐prone. To investigate the role of NIK in αβ T‐cell repertoire formation, we analysed T‐cell development in aly/aly mice bearing a transgenic T‐cell receptor (TCR). Although there were no apparent abnormalities in the mature αβ T cells of non‐transgenic aly/aly mice, the maturation efficiency of idiotype^high+ T cells in the TCR‐transgenic mice was lower in aly/aly mice compared with those found in aly/+ mice, suggesting that the mature αβ T‐cell repertoire could be altered by the absence of functional NIK. In one strain of TCR‐transgenic aly/aly mice with a negatively selecting H‐2 background, the proportion of CD8^low+ idiotype^high+ cells, which are thought to potentially represent the γδ lineage of T cells, was markedly decreased. When the γδ T cells in non‐transgenic aly/aly mice were investigated, the proportion of γδ T cells in the peripheral organs of aly/aly mice was found to be one‐half to one‐fifth of those in aly/+ mice. Analyses of bone marrow chimera mice indicated that NIK in host cells, rather than in donor cells was important for generating a normal number of peripheral γδ T cells. Collectively, these results suggest that NIK could be involved in thymic positive selection of some αβ T cells and that NIK in non‐haematopoietic cells is important for the optimal development and/or maintenance of γδ T cells.     

Clinical, immunohistochemical and phenotypic features of aggressive nodal cytotoxic lymphomas, including α/β, γ/δ T-cell and natural killer cell types

Cytotoxic cells include natural killer (NK) cells and cytotoxic αβ and γδ T lymphocytes (CTLs). These cells express cytotoxic molecules of T-cell restricted intracellular antigen(TIA-1), and activated cytotoxic molecules of perforin, granzyme B, and FasL. Recent studies suggest that most extranodal T-cell lymphomas are derived from CTLs, and that NK cell lymphomas are extranodal. However, only a few nodal NK and cytotoxic lymphomas have been described so far. We present here the clinicopathological features of seven cases of nodal cytotoxic T and NK cell lymphomas. The study excluded anaplastic large-cell lymphomas expressing cytotoxic molecules. The neoplastic cells of all cases contained activated cytotoxic molecules of TIA-1, granzyme B, Fas ligand, and/or perforin. Phenotypically and genotypically, four cases showed αβ T cell type [CD2+, CD3+, T-cell receptor (TCR) δ-1–, βF1+, and TCR gene rearrangement], two cases showed γδ T-cell type [CD2+, CD3+, T-cell receptor (TCR)δ–1+, βF1–, and TCR gene rearrangement], and one case showed NK cell type [CD2+, CD3-, CD56+, T-cell receptor (TCR)δ-1–, βF1–, and TCR gene germline]. Using Southern blot analysis, Epstein-Barr virus (EBV) sequences were detected in six cases, and monoclonal terminal repeat proliferation was confirmed. In addition, in situ hybridization (ISH) studies for EBV showed EBV infection in almost all neoplastic cells. Clinically, all patients presented with peripheral lymphadenopathy in high clinical stages and showed an aggressive course. Hepatosplenomegaly was detected in six cases. During the course of the disease, bone marrow and extranodal invasion were noted in five cases. The nodal type showed an aggressive clinical course in all cases but one, as did the extranodal type. The nodal type varied in phenotype, but was closely associated with EBV infection.