Cytotoxic protein expression in natural killer cell lymphomas and in αβ and γδ peripheral T-cell lymphomas

Lymphomas with T-cell phenotype represent a heterogeneous group of diseases differing in histopathology, tumour site, and cell origin. They include peripheral T-cell lymphomas (PTCLs) derived from αβ cells, but also some recently recognized entities such as γδ hepatosplenic lymphomas and natural killer (NK) cell lymphomas. Only a few studies have investigated the possibility that at least some PTCLs could be derived from lymphocytes with cytotoxic potential. In order to investigate this possibility, 60 cases of PTCL, including 27 cases expressing the αβ T-cell receptor (TCRαβ), 15 TCRγδ cases and 18 cases expressing neither TCR (TCR silent), as well as 14 cases of NK-cell lymphomas, were studied by immunohistochemistry for the expression of TIA-1, perforin, and granzyme B proteins. Expression of TIA-1 is characteristic of cytotoxic cells regardless of their activation status, whereas expression of perforin and granzymes is highly increased in activated cytotoxic cells and correlates with the induction of cytolytic activity. All NK-cell lymphomas (11 sinonasal, three systemic cases) expressed TIA-1, perforin, and granzyme B in most tumour cells. All γδ PTCLs (15 cases) expressed TIA-1 protein in most tumour cells, with a different cytotoxic antigen profile in hepatosplenic γδ PTCL (TIA-1+, perforin−, granzyme B−) and in non-hepatosplenic γδ PTCLs (three nasal, one skin, one lung), the latter expressing the three cytotoxic proteins. Of the 45 cases of αβ and TCR silent PTCL, 15 (33 per cent) were considered to be derived from cytotoxic lymphocytes with expression of at least one cytotoxic protein (TIA-1, 15/45; perforin, 10/41; granzyme B, 14/38) in tumour cells. This cytotoxic protein expression appeared to be related to the site of localization, since 7/13 (54 per cent) extranodal and only 8/32 (25 per cent) nodal αβ and TCR silent PTCLs expressed TIA-1, and to histology, since this pattern was observed in a proportion of anaplastic (6/8, 75 per cent) and pleomorphic (8/17, 47 per cent) lymphomas, but not in AILD-type NHL (0/16). Taken together, our data suggest that NK-cell lymphomas and non-hepatosplenic γδ PTCLs represent tumours of activated cytotoxic NK cells and γδ T cells, respectively; that hepatosplenic γδ PTCLs represent tumours of non-activated cytotoxic γδ T cells; and that a small proportion of αβ and TCR silent PTCLs, mostly extranodal cases, or nodal anaplastic lymphomas, represent tumours of cytotoxic T cells. © 1997 John Wiley & Sons, Ltd.     

Chromosome abnormalities in peripheral T-cell lymphoma

Data on chromosomal abnormalities in T-cell lymphomas are very rare as compared with those reported in B-cell lymphomas. We performed a cytogenetic study in 71 untreated patients with peripheral T-cell lymphoma, classified according to the criteria of the REAL classification. Fifty-seven patients (80.3%) had abnormal clones, whereas 9 karyotypes (12.7%) showed only normal metaphases; 5 karyotypes (7%) could not be analyzed. Recurrent numerical chromosomal abnormalities comprised +3 (21%), +5 (15.7%), +7 (15.5%), +21 (14%), -13 (14%), +8 (12.2%), +19 (12.2%), -10 (10.5%), and -Y (9% of male patients). Chromosomes involved in structural rearrangements were chromosome 6 (31.5%), mainly due to 6q deletions (19.2%), 1q (22.8%), 7q (22.8%), 9p (19.4%), 9q (19.2%), 4q (19.2%), 3q (19.2%), 2p (17.5%), 1p (17.5%), and 14q (17%). Trisomies 3 and 5 mainly correlated with angioimmunoblastic T-cell lymphoma. Isochromosome 7q, associated with trisomy 8, was present in two cases of hepatosplenic gamma/delta T-cell lymphoma. Rearrangements involving the location of T-cell receptor genes were rarely observed (chromosome band 7q35 was rearranged only in three cases, 14q11 in two cases, and 7p15 in none). No correlation could be found between the cytogenetic findings and histologic subgroup or clinical outcome in these patients. Further studies are needed to understand the significance of these abnormalities in peripheral T-cell lymphoma, and to reach a better evaluation of histologic correlations, as many differences persist between the two major classification systems, KIEL and REAL.     

Do Human Peyer's Patches Contribute to the Intestinal Intraepithelial γ/δ T-Cell Population?

T-cell receptor γ/δ? (TcRγ/γ?) lymphocytes in human Peyer's patches (PP) adjoining ileal mucosa were studied by monoclonal antibodies with paired immunofluorescence staining in situ and by flowcytomelric phenotyping of isolated cells. The proportion of γδ? T cells in the follicle-associated epithelium outside the M-cell areas (median 4·I%, range 2·2–30·1%,) was similar to that in mucosal villous epithelium (median 4·4%, range 0·5 30·5%). Most intraepithelial °/δ cells (～90%) expressed CD45RO but only a few expressed CD8 (<10%) and none l-selectin; a dominating subset (median 46%) employed the Vδl/JδI gene product (range 22–100%). The M-cell areas lacked γ/δ cells but contained clustered CD20⁺ andCD3+ lymphocytes. Thesubepithelial PP dome area and interfollicular(T-cell) zones, as well as the mucosal lamina propria. contained very few γ/δ cells (median 1·7%, range 0·4–8·9%) which were dominated (88–100%) by the Vγ 2-encoded subset. Those in the dome area and lamina propria were often (～75%) CD45RO+ (range 44·90%) while very few (～2%) expressed i.-selectin (range 0·15%). By contrast, CD45RO expression on γ/δ cells in the PPT-cell zones was relatively low (～46%) and that of l-selectin relatively high (～43%). In conclusion, TcR γ/δ⁺ cells are quite rare in human PP and belong mainly to the Vδ²-encoded subset, thus being different from most inlraepithelial γδ cells that probably have another origin. The L-selectin ‘fraction of PPγ/δ cells presumably represent newly recruited ‘naïve’ T lymphocytes while CD45RO⁺γ/δ cells both in PP and lamina propria arc probably antigen-primed.     

Incidence of TCR and TCL1 gene translocations and isochromosome 7q in peripheral T-cell lymphomas using fluorescence in situ hybridization

Translocations involving the T-cell receptor (TCR) and TCL1 genes occur in T-cell precursor lymphoblastic leukemia/lymphoma and prolymphocytic leukemia; isochromosome 7q has been associated with hepatosplenic T-cell lymphoma. However, the incidence of these abnormalities in peripheral T-cell lymphomas (PTCLs) as a whole has not been well defined.We studied genetic abnormalities in 124 PTCLs seen at the Mayo Clinic, Rochester, MN, between 1987 and 2007. Tissue microarrays were screened using 2-color break-apart fluorescence in situ hybridization probes flanking the TCRalpha (TCRA, 14q11), TCRbeta (TCRB, 7q35), and TCRgamma (TCRG, 7p15) genes and the TCL1 gene (14q32). Isochromosome 7q was analyzed by using a 2-color probe to 7p and 7q32.1.Translocations involved TCRA in 3 (2.9%) of 102 cases and TCRB in 1 (1%) of 88. Isochromosome 7q was detected in 2 cases of extranodal NK/T-cell lymphoma, nasal type, and 2 cases of anaplastic lymphoma kinase-negative anaplastic large cell lymphoma. One of the latter cases also had a translocation of TCRA, and further studies confirmed a novel t(5;14) translocation.     

γ/δ T cells express a unique surface molecule appearing late during thymic development

The vast majority of T cells in man and mouse use the α/β form of T cell receptor (TcR), and express either CD4 or CD8, whereas the small subset of γ/δ T cells are usually CD4^-CD8^-. In contrast to man and mouse, the γ/δ subset in sheep, defined here using an anti-γ/δ monoclonal antibody (mAb), comprises 30%–60% of T cells. We show that γ/δ T cells in sheep express a unique surface molecule termed T19 which is 215 kDa in size and unrelated to either CD45 or the TcR. The T19 molecule was expressed at a distinct stage during γ/δ T cell ontogeny within the thymus, since γ/δ thymocytes which appeared early in fetal ontogeny were T19^- and also major histocompatibility complex (MHC) class I^- and localized almost exclusively to the outer cortex and cortex of the thymus. “Mature-type” γ/δ thymocytes which emerged late in thymic development were T19⁺ and MHC class I⁺ and localized predominantly to the thymic medulla. The sequence of events indicated that these cells were most likely derived from the early γ/δ thymocytes. These medullary γ/δ thymocytes showed a very distinctive association with Hassall's corpuscles, suggesting a role for these structures in γ/δ thymocyte maturation. In the periphery, T19 was expressed exclusively within the γ/δ T cell subset, however some γ/δ T cells were T19^-. In particular, a large proportion of γ/δ T cells within intestinal epithelium lacked T19, indicating a correlation between T19 expression and either function or homing patterns of γ/δ T cells. Both T19⁺ and T19^- γ/δ T cells were CD2^-, and expressed low levels of LFA-1 and CD5. In addition, γ/δ T cells recirculated differently from other T cells, and appeared not to enter mesenteric lymph nodes at all from the blood. We propose that T19 is a maturation marker for γ/δ T cells. In addition, the exclusive expression of T19 by γ/δ T cells indicates that this molecule most likely serves a fundamental role in the interactions and function of γ/δ T cells.     

Indolent primary cutaneous γ/δ T-cell lymphoma localized to the subcutaneous panniculus and its association with atypical lymphocytic lobular panniculitis

The 2005 classification of lymphoma proposed the designation of subcutaneous panniculitis-like T-cell lymphoma exclusively for those tumors composed of α/β neoplastic cells. Subcutaneous lymphomas that comprised γ/δ T cells are termed primary cutaneous γ/δ T-cell lymphoma. The different clinical outcomes justified this separation; a more indolent course was characteristic of the α/β variants vs the poor 5-year survival of the γ/δ forms. We describe 5 patients with γ/δ T-cell lymphoma localized to the subcutis with a less aggressive clinical course. Two patients were alive 5 years after presentation, and in the remaining 3, the disease is in complete remission after simple intervention. Three patients had a waxing and waning phase, likely representing a prelymphomatous phase, which then progressed to an overt malignant tumor. Therefore, it is important to recognize that not all patients with γ/δ T-cell lymphomas have a poor prognosis.     

Isochromosome 7q in Down syndrome

Isochromosome 7q is not an uncommon chromosomal abnormality. It has been reported in association with Shwachman-Diamond syndrome, Wilms tumor, and hepatosplenic T-cell lymphoma. In other hematolymphoid malignancies, it occurs almost invariably as a secondary change. A notable example is its association with t(4;11)(q21;q23) in acute lymphoblastic leukemia. It has rarely been described in myelodysplastic syndrome and acute myeloid leukemia. We report the occurrence of i(7q) as the primary abnormality in a 2-year-old boy with Down syndrome and minimally differentiated acute myeloid leukemia.     

Contribution of α/β and γ/δ T lymphocytes to immunity against Mycobacterium bovis Bacillus Calmette Guérin: studies with T cell receptor-deficient mutant mice

Mutant mice with defined T cell deficiencies were infected with Mycobacterium bovis bacillus Calmette Guérin (BCG) and the relative contribution of α/β T cells and γ/δ T cells to the host immune response was assessed. Recombinase activating gene (RAG-1)^?/? mutants as well as T cell receptor (TcR) β^?/?, but not TcR-δ^?/?, mutants succumbed to M. bovis BCG infection and failed to develop granulomatous lesions. Antigen-induced IFN-γ production by spleen cells in vitro was abrogated in RAG-1^?/? mutants and markedly diminished in TcR-β^?/? and TcR-δ^?/? mice. Reconstitution experiments suggest that both α/β and γ/δ T cells are essential for antigen-specific IFN-γ secretion. Our data formally prove the crucial role of α/β T cells and reveal accessory functions of γ/δ T cells in optimum immunity against M. bovis BCG.     

Protective role of γ/δ T cells and α/β T cells in tuberculosis

Tuberculosis is a chronic infectious disease which causes major health problems globally. Although acquired resistance crucially depends on α/β lymphocytes, circumstantial evidence suggests that, in addition, γ/δ T lymphocytes contribute to protection against tuberculosis. We have studied Mycobacterium tuberculosis infection in TcR-δ-/- or TcR-β-/- gene deletion mutants which completely lack γ/δ T cells or α/β T cells, respectively. Low inocula of M. tuberculosis led to death of TcR-β-/- mice and transient disease exacerbation in TcR-δ-/- mutants. Infection with higher inocula caused rapid death of TcR-δ-/- mice. The development of and bacterial containment in granulomatous lesions was markedly impaired in TcR-β-/-, and less severly affected in TcR-δ-/- mutants. Mycobacteria-induced IFN-γ production by spleen cells in vitro was almost abolished in TcR-β-/- and virtually unaffected in TcR-δ-/- mice. Our data confirm the crucial role of α/β T cells in protection against established tuberculosis and formally prove a protective role of γ/δ T cells in early tuberculosis.     

Orally induced,peptide-specific γ/δ TCR+ cells suppress experimental autoimmune uveitis

We investigated the role of γ/δ TCR⁺ T cells in induction and suppression of the T cell-mediated disease experimental autoimmune uveitis. Disease induction was studied in Lewis rats perinatally depleted of α/β or γ/δ TCR⁺ subpopulations. Depletion of α/δ TCR⁺ cells completely abrogated disease, whereas treatment with anti-γ/δ antibodies had no influence on onset or intensity of uveitis. However, adoptively transferred γ/δ⁺ cells from orally tolerized rats could mediate suppression of uveitis in an antigen-specific fashion. Uveitis induced by a peptide derived from the uveitogenic retinal soluble antigen (S-Ag) was suppressed by γ/δ⁺ cells from rats orally tolerized with the same peptide as well as HLA peptide B27PD. This disease ameliorating effect could also be observed when rats were fed with the HLA peptide before immunization with S-Ag peptide. Transfer of α/β⁺ T cells from the same donors as well as γ/δ⁺ or α/β⁺ cells from animals fed with control peptide had no ameliorating effect.     

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.     

Characterization of γ/δ T cell clones isolated from human fetal liverand thymus

The origin and development of T cells bearing γ/δ T cell receptors (TcR) has been extensively studied in the mouse. By contrast, little is known about development patterns and diversity of the human γ/δ T cell lineage. To study therepertoire of human γ/δ⁺ T cells during T cell ontogeny, wehave isolated clonal populations of γ/δ⁺ T cells from 14-week fetal thymus and liver and characterized the molecular compositionof their TcR. The technique of in situ hybridization was used to identify cells expressing TcR genes in fetal liver and thymus. A panel of clones representative of developing T cell populations found in vivo was subsequently isolated from both tissues and clones expressing cell surface γ/δ receptors were identified. Although both the liver-derived γ/δ⁺ T cell clone, L2, and the thymus-derived γ/δ⁺ T cell clone, T6, had similar cell surface phenotypes, namely CD3⁺, CD7⁺, CD45⁺ and CD8^?, their reactivity with anti-CD2 and -CD4 antibodies was different. L2 was CD2^high, CD4^? whereas T6 was CD2^low, CD4^low. Both clones possessed effector functions similar to those of adult T cells as demonstrated by the synthesis and secretion of cytokines in response to stimulation through the CD3/TcR complex. Analysis of the TcR composition of the fetal clones showed both clones to possess similar or identical γ chain components, C_γ1, J_γ1/2, V_γ8, and both utilize V_δ gene segments other than V_δ1. This TcR genotype has not been previously reported in the analysis of adult γ/δ⁺ T cells. Our studies have identified a unique population of human γ/δ⁺ T cells that may be derived extrathymically and appear to be preferentially and perhaps transiently expressed during fetal life.     

Expression of cyclin-dependent kinase 6 (cdk6) and frequent loss of CD44 in nasal-nasopharyngeal NK/T-cell lymphomas: comparison with CD56-negative peripheral T-cell lymphomas

Lymphomas involving the nasal and nasopharyngeal region mainly include CD56-positive natural killer (NK)/T-cell lymphomas, CD56-negative peripheral T-cell lymphomas (PTL), and B-cell lymphomas. Among these, the CD56-positive lymphoma, presumably of an NK/T-cell nature, is frequently seen in Asian, Mexican, and South American patients. NK cells are proposed to be closer developmentally to T cells than to other lymphoid cells, because bipotential common progenitor cells of NK/T-cell lineage have been isolated. In this study, we collected 47 cases of nasal lymphoma and investigated the phenotypic difference between NK/T-cell lymphoma and PTL by examining the pattern of the developmentally differentially expressed molecules cdk6 (cyclin-dependent kinase 6), CD44, CD117, and by examining the rearrangement of the T-cell receptor gene (TcR-GR). cdk6, an essential regulator of the cell cycle in G1 progression, was over-expressed in a subset of cortical thymocytes, but absent in mature thymocytes. In contrast, CD44, a glycosylated adhesion molecule, was absent in cortical thymocytes, but present in mature thymocytes and peripheral activated T cells. We found both over-expression of nuclear cdk6 (n-cdk6) and frequent absence of CD44 in nasal CD56-positive NK/T-cell lymphomas, in contrast to most nasal CD56-negative PTL, which were CD44-immunoreactive with weak or no expression of n-cdk6. Almost all tested cases of NK/T-cell lymphoma displayed a germ-line configuration of TcR, without evidence of gene rearrangement. Thus, there seems to be a useful distinction between the classical NK/T type of nasal lymphoma (CD56+/n-cdk6+/CD44-/TcR-GR-) and PTL (CD56-/n-cdk6-/CD44+/TcR-GR+) involving the nasal region. The presence of Epstein-Barr virus does not seem to be a good marker for distinguishing between NK/T lymphoma and PTL involving the nasal region.     

Tissue microarray-based screening for chromosomal breakpoints affecting the T-cell receptor gene loci in mature T-cell lymphomas

The pathogenesis of mature T-cell non-Hodgkin lymphomas (T-NHLs) is poorly understood. Analogous to B-cell lymphomas, in which the immunoglobulin (IgH) receptor loci are frequently targeted by chromosomal translocations, the T-cell receptor (TCR) gene loci are affected by translocations in a subset of precursor T-cell malignancies. In a large-scale analysis of 245 paraffin-embedded mature T-NHLs, arranged in a tissue microarray format and using improved FISH assays for the detection of breakpoints in the TCRalpha/delta, TCRbeta, and TCRgamma loci, we provide evidence that mature T-NHLs other than T-cell prolymphocytic leukaemia (T-PLL) also occasionally show a chromosomal rearrangement that involves the TCRalpha/delta locus. In particular, one peripheral T-cell lymphoma (not otherwise specified, NOS) with the morphological variant of Lennert lymphoma displayed a chromosomal translocation t(14;19) involving the TCRalpha/delta and the BCL3 loci. A second case, an angio-immunoblastic T-cell lymphoma (AILT), carried an inv(14)(q11q32) affecting the TCRalpha/delta and IgH loci. FISH signal constellations as well as concomitant comparative genomic hybridization (CGH) data were also suggestive of the occurrence of an isochromosome 7, previously described to be pathognomonic for hepatosplenic T-cell lymphomas, in rare cases of enteropathy-type T-cell lymphoma.     

Mechanisms determining cell membrane expression of different γδ TCR chain pairings

We investigated the ability of the most common TCR‐γ and δ chains to express on the cell surface. Vγ1Cγ4 and Vγ7Cγ1 chains paired with all TCR‐δ chains tested, whereas Vγ4Cγ1 chains were found with Vδ4 and Vδ5, but not with Vδ2 or Vδ6 chains, and Vγ2Cγ2 chains were expressed only with Vδ5. Mapping studies showed that up to four polymorphic residues influence the different co‐expressions of Vγ1 and Vγ2 chains with Vδ chains. Unexpectedly, these residues are not located in the canonical γ/δ interface, but in the outer part of the γδ TCR complex exposed to the solvent. Expression of functional Vδ4 or Vδ6 chains in Vγ2/Vδ5⁺ cells or of functional Vγ2Cγ2 in Vγ1⁺ cells reduced cell‐surface expression of the γδ TCR. Taken together, these data show that (i) the Vγ/Vδ repertoire of mouse γδ T cells is reduced by physical constraints in their associations. (ii) Lack of Vγ2/Vδ expression is due to the formation of aberrant TCR complexes, rather than to an intrinsic inability of the chains to pair and (iii) despite not being expressed at the cell surface, the presence of a functionally rearranged Vγ2 chain in γδ T cells results in reduced TCR levels.     

Hepatosplenic γδ T-cell lymphoma with ring chromosome 7, an isochromosome 7q equivalent clonal chromosomal aberration

Hepatosplenic T-cell lymphoma is a rare, clinically aggressive lymphoma. Most cases represent a neoplasm of mature non-activated γδ T cells. Isochromosome 7q i(7)(q10) is thought to be the primary cytogenetic abnormality of this disease. In this paper, we describe a hepatosplenic γδ T-cell lymphoma case, with clonal ring chromosome 7 exemplifying an isochromosome 7q equivalent clonal aberration. A 62-year-old female patient presented with thrombocytopenia, isolated hepatosplenomegaly, and extremely high levels of LDH. Bone marrow work-up demonstrated a sinusoidal cytotoxic T-cell infiltrate with blastic features, while molecular studies verified monoclonal rearrangement for both TCR γ and TCR δ genes. Cytogenetics revealed clonal abnormalities including ring chromosome 7, trisomy 8, and der(19), while FISH analysis detected 7q amplification with partial deletion of 7p in ring chromosome 7. To the best of our knowledge, this is the first reported T-cell lymphoma case with ring chromosome 7.     

Sequential appearance of γ/δ- and α/β-bearing T cells in the peritoneal cavity during an i.p. infection with Listeria monocytogenes

To search for a potential role of T cell antigen receptor (TcR) γ/β-bearing cells in host-defense against Listeria monocytogenes, we analyzed the sequential appearance of γ/δ and α/β T cell in the peritoneal exudate cells (PEC) during an i.p. infection with sublethal dose (2 × 10³) of viable Listeria organisms in mice. The PEC on day 1 after the infection consisted of 48% macrophages and 50% lymphocytes, most of which were surface IgM⁺ (B) cells. The number of PEC increased to the maximal level by day 3. The PEC at this stage contained an appreciable number of CD3⁺ T cells in addition to a large number of macrophages. Of the CD3⁺ cells, the proportion of CD4^?CD8^? cells, most of which expressed no TcR α/β, increased to the maximal level on day 3 after the infection. In correlation with an increased number of CD3⁺CD4^?CD8^?TcR α/β^? cells, high level of TcR γ/δ chain gene messages was detected in the nonadherent population of the PEC on this stage. On the other hand, the PEC on day 8 contained an increased number of CD4⁺CD8^? and CD4^?CD8⁺ cells which expressed TcR α/β chain on their surface. These results suggest that the γ/δ T cells precede the α/β T cells in appearance during listerial infection. The γ/β T cells may be involved at the first line of the host-defense against Listeria.     

Phosphate is essential for stimulation of Vγ9Vδ2 T lymphocytes by mycobacterial low molecular weight ligand

T lymphocytes are divided into two subsets which express different T cell receptor heterodimers. In the peripheral blood of healthy individuals, the majority of T cells express the α/β T cell receptor (> 90%) while a minority have the γ/δ T cell receptor (< 10%). The γ/δ T cells of adults use preferentially the Vγ9Vδ2 chain combination. Although the stimulation requirements for γ/δ T lymphocytes are still undetermined, it has been reported that γ/δ T cells are not only stimulated, like α/β T cells, by conventional protein antigens and superantigens, but also by unusual ligands. Mycobacteria selectively stimulate Vγ9Vδ2 T cells, and a nonproteinacious low molecular weight fraction of 1–3 kDa has been identified as the tentative active component. Here, we confirm the nonproteinacious nature of this ligand, and show that it is comprised of unusual carbohydrate and phosphate. Importantly, cleavage of the terminal phosphate by alkaline phosphatase completely abrogates the stimulatory activity of the low molecular weight ligand for Vγ9Vδ2 T cells. Even mycobacterial whole lysate loses its stimulatory activity, for this T cell subset, after dephosphorylation with alkaline phosphatase. These findings identify phosphocarbohydrates as a novel molecular entity with selective stimlatory activity for a defined T cell subset.     

Peripheral T/NK-cell lymphoma: a report of the IXth Workshop of the European Association for Haematopathology

AIMS: In April 1998, The European Association for Haematopathology organized the IXth workshop on peripheral T-cell and NK-cell lymphomas and leukaemias. The workshop focused on unusual subtypes of these rare malignancies, allowing evaluation of the recently published WHO classification of neoplastic diseases of the lymphoid tissues. METHODS AND RESULTS: One-hundred and three cases were centrally immunophenotyped and hybridized for EBER1/2 of Epstein--Barr virus. All cases were reviewed by a panel of experienced haematopathologists and classified according to the new WHO classification for lymphoid neoplasms. Three cases were considered as precursor T-cell and 95 cases as peripheral T/NK-cell lymphoma/leukaemia. Although the cases represented a selected series of unusual cases, the following conclusions could be made: (i) Most lymphomas except the hepatosplenic gamma/delta T-cell lymphomas showed a rather broad morphological spectrum, with differences both between and within individual tumours. (ii) This heterogeneity was also reflected by the immunophenotype, for instance a variable expression of CD30 was found in many enteropathy type T-cell lymphomas. (iii) Exceptions in phenotype were regularly found in almost all categories, indicating that phenotype should not be the final determining factor in classification. (iv) The great majority of T-cell lymphomas expressed the alpha/beta T-cell receptor, with the exception of all but one hepatosplenic T-cell lymphomas and a few other extranodal peripheral T cell lymphomas. (v) Malignancies of precursor cells, blastic NK-cell lymphoma/leukaemia, adult T-cell lymphoma/leukaemia and most AIL-type T-cell lymphomas did not express cytotoxic molecules such as TIA1 and granzyme-B. In contrast, all five aggressive NK/T-cell lymphomas/leukaemias, a single case of large granular lymphocyte leukaemia and 40 of 47 primary extranodal lymphoma/leukaemias expressed these molecules. In hepatosplenic gamma/delta T-cell lymphoma, five of six cases showed expression of TIA1 but not of granzyme-B. (vi) Seven tumours developed after organ-transplant, four cases being EBV-positive. No distinct phenotype could be attributed to these cases. CONCLUSIONS: Most peripheral T/NK cell lymphomas could be categorized as distinct entities as described in the recently proposed WHO classification for lymphoid neoplasms.     

Hepatosplenic and other gammadelta T-cell lymphomas

The 2005 Society for Hematopathology/European Association for Haematopathology Workshop session 11 was dedicated to hepatosplenic T-cell lymphoma (HSTCL). HSTCL is a rare aggressive type of extranodal lymphoma characterized by hepatosplenomegaly, bone marrow involvement, and peripheral blood cytopenias. HSTCL exhibits a distinctive pattern of infiltration; tumor cells preferentially infiltrate the sinusoids of the splenic red pulp, liver, and bone marrow. The tumor cells have a nonactivated cytotoxic T-cell immunophenotype and frequently carry a recurrent cytogenetic abnormality, isochromosome 7q. Most cases express the gammadelta T-cell receptor, but cases can have an alphabeta phenotype and are considered to be a variant of the disease. Although HSTCL is the prototype peripheral T-cell lymphoma expressing the gammadelta T-cell receptor, non-HSTCL proliferations of gammadelta T cells can involve other extranodal sites, mainly skin and mucosa. These gammadelta T-cell lymphomas display marked heterogeneity in clinical and histologic features. In contrast with HSTCL, non-HSTCL gammadelta T-cell lymphomas frequently have an activated cytotoxic phenotype and most likely are not a single disease entity.