Clonal populations of CD4+ and CD8+ T cells in patients with multiple myeloma and paraproteinemia

Patients with paraproteinemia have abnormalities in their T-cell subsets including inversion of the CD4:CD8 ratio and increased expression of activation markers. Recently, distortions in T-cell receptor (TCR) TCRAV and TCRBV gene segment expression have been reported, although the significance of these observations is unclear given the finding of clonal populations of CD8+ T cells in healthy elderly individuals. We have used an extensive range of TCR V-region- specific monoclonal antibodies to assess TCRAV and TCRBV expression in patients with myeloma and paraproteinemia. TCR sequence analysis was used to assess the clonality of expansions and 3-color fluorescence- activated cell sorting analysis determined the phenotype of the expanded populations. The patients show novel oligoclonal expansions within the CD4+ subset and show an increased frequency of CD8+ expansions. Oligoclonal CD4+ T cells belong to the rare CD4+CD28- T- cell subset, a phenotype associated with granular morphology. CD45RA and CD11b are expressed on many of the CD8 T-cell expansions. Comparison of T-cell receptor sequences from two T-cell clones in one patient suggests a possible role for a common peptide antigen in the generation of the expansions. Further work is needed to identify the relevance of such T cells to the B-cell proliferation.     

CD21 antigen in T-lineage neoplastic lymphoid cells: Characteristic expression at thymic stage

The expression of CD21 antigen, a receptor for the C3d fragment of complement and Epstein-Barr vlrus (EBV), was Investigated in a total of 85 cases of neoplastic lymphoid cells Including 39 cases of T-lineage acute lymphoblastic leukemia (ALL)/lymphoblastic lymphoma (LBL), although CD21 antigen is usually regarded as a pan-B antigen. The CD21 antigen was expressed by one of the eight cases of neoplastic lymphoid cells expressing the CD7 antigen as a sole pan-T antigen, by three of the 20 cases of pro- or early thymic stage (CD7+ CD5+ CD2-, CD7+ CD5- CD2+, or CD7+ CD5+ CD2+), and ten of 11 cases of thymic stage (CD3r CD4+ CD8+), but not by one case of late thymic stage (CD3 ± CD4+ CD8-) T-ALULBL cells. The CD21 antigen was not expressed by any of the 11 cases of adult T-cell leukemia (ATL) or two cases of chronic T-lineage leukemia. At most 4% of the normal thymocytes obtained from seven infants or children expressed the CD21 antlgen. While only a very limited population of normal thymocytes expresses CD21 antigen, T-ALL/LBL cells at the thymic stage characteristically express CD21 antigen in contrast to pro- or early thymic ALL/LBL or peripheral-stage neoplastic T cells. The estimation of the expression of CD21 antigen is useful for delineating stages of differentiation in T-ALL/LBL. Furthermore, these observation are notable, considering the possibiilty that the reported EBV-carrying T-cell lymphomas result from the penetration of EBV into EBV-negative neoplastic T cells. © 1994 Wiley-Liss, Inc.     

Constitutive expression of B7 restores immunogenicity of tumor cells expressing truncated major histocompatibility complex class II molecules.

The inability of the autologous host to reject resident tumor cells is frequently the result of inadequate generation of tumor-specific T cells. Specific activation of T cells occurs after delivery of two signals by the antigen-presenting cell. The first signal is antigen-specific and is the engagement of the T-cell antigen receptor by a specific major histocompatibility complex antigen-peptide complex. For some T cells, the second or costimulatory signal is the interaction of the T-cell CD28 receptor with the B7 activation molecule of the antigen-presenting cell. In the present study, we demonstrate that mouse sarcoma cells genetically engineered to provide both T-cell activation signals stimulate potent tumor-specific CD4+ T cells that cause rejection of both engineered and wild-type neoplastic cells. Two other recent studies have also demonstrated that costimulation via B7 can improve tumor immunity. However, our study differs from these reports by two important observations. (i) One of these studies utilized mouse tumor cells expressing xenogenic viral antigens, and hence, the results are not applicable to wild-type resident tumors. Our study, however, demonstrates that coexpression of B7 by major histocompatibility complex class II+ tumor cells induces immunity in the autologous host that is specific for naturally occurring tumor antigens of poorly immunogenic tumors. (ii) In both earlier studies, only CD8+ T cells were activated after coexpression of B7, whereas in the present report, tumor-specific CD4+ T cells are generated. This report therefore illustrates the role of B7 activation molecule in stimulating potent tumor-specific CD4+ T cells that mediate rejection of wild-type tumors and provides a theoretical basis for immunotherapy of established tumors.     

De novo expression of killer immunoglobulin-like receptors and signaling proteins regulates the cytotoxic function of CD4 T cells in acute coronary syndromes

The inflammatory infiltrate in atherosclerotic plaque is composed of T cells and macrophages. CD4+ T cells with a unique phenotype, CD4+CD28null, are preferentially recruited into culprit lesions. These T cells are distinct from classic CD4+CD28+ T cells in gene expression and function, including their ability to mediate cytolysis. In this study, we have investigated the regulation of CD4+CD28null T-cell cytolytic function. In patients with acute coronary syndromes (ACS), CD4+CD28null T cells express killer immunoglobulin-like receptors (KIRs). KIRs encompass a polymorphic family of receptors that recognize HLA class I molecules and have been implicated in self-tolerance. CD4+CD28null T-cell clones from patients with ACS and age-matched controls were compared for their KIR-expression profile. T-cell clones derived from the patients expressed a broader spectrum of KIRs (P<0.001) with preference for the stimulatory variant, CD158j. Additionally, CD4+ T-cell clones from patients but not those from controls acquired de novo expression of the DAP12 molecule, an adapter chain that transmits CD158j-derived signals. Cumulative expression of CD158j and DAP12 endowed cytolytic competence on CD4+CD28null T cells, allowing them to kill in the absence of T-cell receptor triggering. Our data demonstrate that CD4+CD28null T cells in ACS are characterized by a unique gene expression profile. Consequently, these T cells acquire cytolytic capability that can bypass the need for T-cell receptor triggering and, thus, impose a threat to self-tolerance.     

Leucocyte-specific protein (LSP1) in malignant lymphoma and Hodgkin's disease

Biopsies from 319 haematopoietic neoplasms were immunostained for intracellular leucocyte-specific protein 1 (LSP1) to assess its distribution and to compare its diagnostic value with that of CD45 (leucocyte common antigen: LCA). Most small B-cell neoplasms expressed LSP1, but one third of diffuse large B-cell lymphomas (DLBCL) were LSP1 negative. Among the cases with DLBCL (76 samples) tested for both LSP1 and CD45, one fifth expressed only CD45, but five samples were LSP1-positive and negative for CD45. The latter pattern was also seen in four of nine myelomas. Five out of 14 T-lymphoblastic lymphomas co-expressed LSP1 and CD45, and three cases were LSP1 negative and CD45-positive. Most peripheral T-cell lymphomas co-expressed LSP1 and CD45. All anaplastic lymphoma kinase (ALK)-negative lymphomas of anaplastic large cell morphology (T and null phenotype) expressed LSP1 although the percentage of LSP1-positive tumour cells was variable, however, only seven out of 30 cases with ALK-positive lymphoma were LSP1 positive. LSP1 was expressed on Reed-Sternberg cells in 60 out of 66 cases with classic Hodgkin's disease but neoplastic cells were usually negative in lymphocyte predominant Hodgkin's. This study confirms the wide expression of LSP1 within haematopoietic neoplasms and its diagnostic value for a minority of lymphoid tumours that have lost CD45 expression. Furthermore, the strong expression of LSP1 in classic Hodgkin's disease, contrasting with its heterogeneous expression in ALK-negative anaplastic lymphomas, may help to distinguish the latter lymphomas from patients with tumour cell-rich Hodgkin's disease.     

Definition of a population of CD4-8- T cells that express the alpha beta T-cell receptor and respond to interleukins 2, 3, and 4.

Whereas most T cells express surface CD4 or CD8 molecules, a minority lacks both. CD4-8- cells usually express the gamma delta T-cell receptor, but here we describe a population of CD4-8- T cells from the peripheral blood that express the alpha beta heterodimer. These cells have different surface antigens than gamma delta+ T cells, expressing CD5 but lacking CD16, and differ in function from gamma delta+ T cells. CD4-8- alpha beta+ cells lack non-major histocompatibility complex-restricted cytolytic function but can be induced to lyse their target cells after activation of their T-cell receptors. A peculiar characteristic of these cells is their responsiveness to interleukin 3. Since these cells have not altered their phenotype or function over a 12-month period in culture, they appear to be mature T cells. The results indicate that normal human peripheral blood contains two subsets of CD4-8- T cells, expressing either gamma delta or alpha beta receptors, that differ in function, phenotype, and growth control.     

New differentiation pathway for double-negative regulatory T cells that regulates the magnitude of immune responses

Recent studies have demonstrated that in peripheral lymphoid tissues of normal mice and healthy humans, 1% to 5% of alphabeta T-cell receptor-positive (TCR(+)) T cells are CD4(-)CD8(-) (double-negative [DN]) T cells, capable of down-regulating immune responses. However, the origin and developmental pathway of DN T cells is still not clear. In this study, by monitoring CD4 expression during T-cell proliferation and differentiation, we identified a new differentiation pathway for the conversion of CD4(+) T cells to DN regulatory T cells. We showed that the converted DN T cells retained a stable phenotype after restimulation and that furthermore, the disappearance of cell-surface CD4 molecules on converted DN T cells was a result of CD4 gene silencing. The converted DN T cells were resistant to activation-induced cell death (AICD) and expressed a unique set of cell-surface markers and gene profiles. These cells were highly potent in suppressing alloimmune responses both in vitro and in vivo in an antigen-specific manner. Perforin was highly expressed by the converted DN regulatory T cells and played a role in DN T-cell-mediated suppression. Our findings thus identify a new differentiation pathway for DN regulatory T cells and uncover a new intrinsic homeostatic mechanism that regulates the magnitude of immune responses. This pathway provides a novel, cell-based, therapeutic approach for preventing allograft rejection.     

Coexpression of T- and B-markers in a lymphoproliferative disorder

An atypical case of lymphoproliferative disorder in which T- and B-cell antigens were coexpressed in the neoplastic cells is described. The disease was characterised by hepatosplenomegaly, lymphadenopathy, a low WBC (5 X 10(9)/l) and bone marrow infiltration. The predominant cell population (greater than 70%) comprised lymphoid cells with a range of nuclear irregularities and included some blast cells. 90% of the peripheral blood lymphocytes showed a mature T-helper phenotype (E+, T11+, T3+, T4+, T8-, T6-, TdT-) with coexpression of the specific B-markers B1 and FMC7, in 90% and 50% of cells, respectively. HLA-DR antigens were present in 55% of cells while surface and cytoplasmic immunoglobulins (Ig) were detected in less than 10% of cells. Molecular investigations with appropriate probes showed evidence of T-cell receptor gene rearrangement but no rearrangement for the genes of the Ig-heavy and -light chains. Cytogenetic studies revealed a translocation t(10;19) (p12; q13) in all the metaphases analyzed. This case demonstrates that the study of neoplastic cells with a battery of monoclonal antibodies may disclose the existence of a hitherto unrecognised lymphoid cell population with atypical expression of B- and T-cell antigens. On the other hand, the presence of T-cell receptor gene rearrangement indicates that this is a T-cell disorder with the aberrant co-expression of specific B-cell markers.     

Functional abnormalities of CD8+ T cells define a unique subset of patients with common variable immunodeficiency

A substantial subgroup of patients with common variable immunodeficiency (CVI) exhibit an abnormal T-cell phenotype characterized by a low CD4/CD8 ratio associated with a significant increase in the absolute number of CD8+ T cells (CVI4/8low patients). In the present study, we examined the phenotypic and functional properties of purified T-cell subsets in this group of CVI patients. CD8+ T cells from CVI4/8low patients manifested increased expression of HLA-DR and CD57 and decreased expression of CD45RA as compared with CD8+ T cells from normal controls. When stimulated with anti-CD3 and phorbol 12-myristate 13-acetate, purified patient CD8+ T cells exhibited significantly decreased proliferation, c-myc expression, and interleukin-2 (IL-2) production compared with that of normal CD8+ T cells. Nevertheless, mitogen-activated patient CD8+ T cells secreted elevated amounts of gamma-interferon and IL-5 and normal amounts of IL- 4. This abnormal pattern of proliferation and cytokine production was limited to the CD8+ T-cell subset as CD4+ T cells from these patients exhibited normal proliferation and cytokine production. In further functional studies, purified CD8+ T cells from CVI4/8low patients manifested increased cytotoxic T-lymphocyte activity and suppressor activity, as compared with normal CD8+ T cells, when they were tested in (1) an anti-CD3 "redirected" cytotoxicity assay and (2) a suppressor assay consisting of CD8+ T cells and Staphylococcus aureus Cowan I (SAC) plus IL-2-stimulated normal (allogeneic) B cells. In the latter case, patient CD8+ T cells suppressed IgG production, but not IgM production. Finally, in studies to evaluate the role of patient CD8+ T cells in the pathogenesis of hypogammaglobulinemia, we determined the capacity of SAC and IL-2 to induce Ig production in highly purified patient B cells, ie, in the absence of patient CD8+ T cells. We found that, whereas B cells from one patient produced normal amounts of IgG, B cells from three patients were unable to produce normal amounts of IgG under these conditions. These data establish the phenotypic and functional characteristics of CD8+ T cells in CVI4/8low and clearly distinguish CVI4/8low patients from other patients with this syndrome. The data do not support the contention that hypogammaglobulinemia in CVI4/8low patients is due to a direct effect of CD8+ T cells on terminal B-cell differentiation, except in the occasional patient. The abnormal CD8+ T cells may, nevertheless, have more subtle effects of lymphoid function that play a role in disease pathogenesis.     

Establishment and characterization of a mouse strain (TLL) that spontaneously develops T-cell lymphomas/leukemia

In this study, a mouse strain (TLL) that spontaneously develops T-cell lymphomas/leukemia with an early onset and high incidence was established and characterized. All tumors analyzed were found to express the alpha,beta T-cell receptor, and the majority of them had a mature, CD3+CD4+CD8- immunophenotype. In a few cases, tumors with a more immature CD3+CD4+CD8+ phenotype were isolated. Expanded phenotyping using a broad panel of lymphocyte differentiation markers confirmed the mature T-cell phenotype of the tumors. Histologic and cell cycle analysis of the tumors revealed an aggressive lymphoblastic malignancy with a very high proliferation rate and widespread engagement of bone marrow and lymphoid as well as nonlymphoid organs. Thus, the TLL mouse strain represents a unique model for the analysis of the oncogenesis and progression of mature T-cell tumors and for the development of therapeutic measures to combat such tumors.     

Expression of the c-kit receptor in human lymphomas is restricted to Hodgkin's disease and CD30+ anaplastic large cell lymphomas

The product of the proto-oncogene c-kit is a transmembrane receptor protein that plays an important role in the regulation of normal and neoplastic hematopoiesis via the interaction with its specific ligand termed stem cell factor. To examine whether c-kit product is possibly involved in the pathogenesis of human lymphomas, we analyzed the expression of the c-kit protein in neoplastic cells from a variety of lymphoid tumors by immunostaining of lymph node frozen sections with the 17F11 antibody, detecting an extracellular epitope of the c-kit receptor, and of c-kit RNA by Northern blot hybridization. Of 24 nonHodgkin's lymphomas (NHL) of B- and T-cell phenotype, none expressed immunodetectable c-kit protein that was also not evidenced in lymphoid cells of reactive lymph nodes and normal tonsils. In contrast, c-kit protein was expressed by Reed-Sternberg cells and their mononuclear variants from 11 of 21 Hodgkin's disease (HD) cases, and in tumor cells from 11 of 16 cases of CD30+ anaplastic large cell lymphoma (ALCL). c- kit specific mRNA was also detected in lymph node tissues from HD and ALCL cases but not in neoplastic tissues from NHL other than ALCL. In addition, c-kit/CD30+ tumor cells were evidenced by flow cytometry in a patient displaying massive bone marrow involvement by ALCL. With the exclusion of lymphocyte predominance cases of HD that resulted c-kit expression and the other histologic subtypes of HD or the immunologic phenotype of tumor cells (B, T, nonB-nonT) in both HD and ALCL. The highly restricted expression of the c-kit product among human lymphomas to HD and ALCL provides a further biologic link between these two closely related lymphoma entities.     

Transgenic mice carrying the diphtheria toxin A chain gene under the control of the granzyme A promoter: expected depletion of cytotoxic cells and unexpected depletion of CD8 T cells.

We have generated transgenic mice bearing the diphtheria toxin A chain (DTA) gene under the control of granzyme A (GrA) promoter sequences (GrA-DTA). GrA is expressed in activated cytotoxic cells but not in their immediate progenitors. These GrA-DTA mice are deficient in cytotoxic functions, indicating that most cytotoxic cells express GrA in vivo. Surprisingly, one founder strain containing a multicopy GrA-DTA insert show a marked and selective deficiency in CD8+ cells in peripheral lymphoid organs. This depletion was not observed in thymus, where the distribution of CD4+ and CD8+ cells is normal. Moreover, the emigration of T cells from thymus is normal, indicating that the depletion occurs in the periphery. GrA-DTA mice should be useful as models to dissect the role of cytotoxic cells in immune responses and as recipients of normal and neoplastic hematopoietic cells. The selective depletion of CD8+ cells in one founder strain could have implications for postthymic T-cell development.     

CD8+CD28-, suppressive T cells in systemic lupus erythematosus

Recent studies show that a CD8+CD28- phenotype of T-cell population inhibits the reactivity of T-helper cells either by a contact-dependent mechanism or with secreting suppressive cytokines. In this study, we have explored the peripheral blood CD8+CD28- T-cell population in 53 patients with systemic lupus erythematosus (SLE) in comparison to healthy and diseased control groups. The distribution of CD28- cells within CD8+ population has been found significantly lower in patients with SLE than in healthy individuals. While there were no significant differences in the expression of costimulatory molecules CD80 and CD86, the CD40 expression on monocytes was found significantly lower and there was a slight decrease of expression of Interleukin-10 (IL-10) in CD8+CD28- population in patients with SLE. The Transforming growth factor-beta (TGF-beta) mRNA expression was found higher in CD8+CD28- T cells. Neither activation induced nor time-dependent change in the frequency of CD8+CD28- cells has been observed following stimulation at various time-points indicating that the control of CD28 expression was not dependent on the presence of sustained stimulations. Decrease in CD8+CD28- T cells which normally produce TGF-beta and their low-level IL-10 content may reflect impaired T-cell suppression and accordingly, increased T cell help to autoreactive B cells in patients with SLE.     

T-cell lineage commitment and cytokine responses of thymic progenitors

The earliest steps of intrathymic differentiation recently have been elucidated. It has been reported that both CD4lo (CD44+ CD25- c-kit+ CD3- CD4lo CD8-) and pro-T cells (CD44+ CD25+ c-kit+ CD3- CD4- CD8-, representing the next step in maturation) exhibit germline T-cell receptor beta and gamma loci, suggesting that neither population is exclusively committed to the T-cell lineage. Several groups have shown that CD4lo cells retain the capacity to generate multiple lymphoid lineages in vivo; however, the lineage commitment status of pro-T cells is unknown. To determine when T-cell lineage commitment occurs, we examined the ability of sorted CD4lo and pro-T cells to generate lymphoid lineage cells in vivo or in fetal thymic organ cultures (FTOCs). When intravenously injected into scid mice, CD4lo cells generated both T and B cells, whereas the progeny of pro-T cells contained T cells exclusively. Fetal thymic organ cultures repopulated with CD4lo cells contained both T and natural killer (NK) cells, whereas cultures repopulated with pro-T cells contained T cells almost exclusively. These observations strongly suggest that T-cell lineage commitment occurs during the transition of CD4lo to pro-T cells. Because it is likely that the thymic microenvironment plays a critical role in T-cell commitment, we compared the responses of CD4lo and pro-T cells to various cytokine combinations in vitro, as well as the ability of the cultured cells to repopulate organ cultures. Cytokine combinations that maintained T-cell repopulation potential for both CD4lo and pro-T cells were found. CD4lo cells proliferated best in response to the combination containing interleukin-1 (IL-1), IL-3, IL- 6, IL-7, and stem cell factor (SCF). Unlike CD4lo cells, pro-T cells were much more dependent upon IL-7 for proliferation and FTOC repopulation. However, combinations of cytokines lacking IL-7 were found that maintained the T-cell repopulating potential of pro-T cells, suggesting that, whereas this cytokine is clearly very important for normal pro-T cell function, it is not an absolute necessity during early T-cell expansion and differentiation.     

Modulation of tryptophan catabolism by human leukemic cells results in the conversion of CD25- into CD25+ T regulatory cells

Indoleamine 2,3-dioxygenase (IDO) is a novel immunosuppressive agent expressed in some subsets of normal and neoplastic cells, including acute myeloid leukemia (AML) cells. Here, we show that IDO expression correlates with increased circulating CD4+CD25+FOXP3+ T cells in patients with AML at diagnosis. In vitro, IDO+ AML cells increase the number of CD4+ CD25+ T cells expressing surface CTLA-4 and FOXP3 mRNA, and this effect is completely abrogated by the IDO inhibitor, 1-methyl tryptophan (1-MT). Purified CD4+CD25+ T cells obtained from coculture with IDO+ AML cells act as T regulatory (T(reg)) cells because they do not proliferate, do not produce interleukin (IL)-2, and inhibit naive T-cell proliferation. Coculture with IDO+AML cells results in the conversion of CD4+CD25- into CD4+CD25+ T cells, which is completely abrogated by 1-MT. Moreover, in mice, intrasplenic injection of IDO+ leukemia/ lymphoma A20 cells induces the expansion of bona fide T(reg) cells by conversion of CD4+CD25- T cells; this effect is counteracted by 1-MT treatment. These data indicate that AML cells induce T-cell tolerance by directly converting CD4+CD25- T cells into CD4+CD25+ T(reg) cells through an IDO-dependent mechanism.     

SIV-specific CD8+ T cells express high levels of PD1 and cytokines but have impaired proliferative capacity in acute and chronic SIVmac251 infection

Programmed death-1 (PD-1) is a critical mediator of virus-specific CD8+ T-cell exhaustion. Here, we examined the expression of PD-1 on simian immunodeficiency virus (SIV)-specific CD8+ T cells and its possible involvement in regulation of cytokine production, proliferation, and survival of these cells. The majority of SIV-specific CD8+ T cells expressed a PD-1(high) phenotype, independent of their differentiation status, in all tissues tested. PD-1 expression gradually declined on CD8+ T cells specific for SIV-derived epitopes that had undergone mutational escape, indicating that antigen-specific TCR stimulation is the primary determinant of PD-1 expression. SIV-specific PD-1(high)CD8+ T cells produced IFN-gamma, TNF-alpha, and IL-2 under cognate peptide stimulation. While CD8+ T cells that proliferated in response to antigen had a PD-1(high) phenotype, it was determined that there was a reduced proliferative capacity of PD-1(high) compared with PD-1(low) SIV-specific CD8+ T cells. PD-1(high) SIV-specific CD8+ T cells were highly susceptible to cell death leading to loss of such cells after in vitro stimulation. Thus, PD-1 is a negative regulator of SIV-specific CD8+ T cells, operating predominantly through the induction of cell death. Manipulation of the interaction of PD-1 with its ligands could thus potentially restore the CD8+ T-cell responses in SIV infection.     

An immunoregulatory function for the CD8 molecule.

The molecular details of immunoregulatory phenomena associated with CD8+ T lymphocytes have not been clearly elucidated. We tested the hypothesis that the cell surface glycoprotein CD8 is itself essential in mediating the inhibitory effects associated with CD8+ T cells. For this purpose we utilized a T-cell clonal pair, consisting of a human CD8+ T-cell clone and a specific CD8- phenocopy of this clone obtained via antisense RNA mutagenesis, to modulate allogeneic responses in vitro. Our findings indicate that the expression of the CD8 molecule by the inhibitory cells is essential for down-regulation of both allogeneic proliferation and generation of cytotoxicity in mixed lymphocyte cultures. These results define an immunomodulatory function for the CD8 molecule and provide insights into the molecular basis of immunosuppression.     

Large granular lymphocytic leukaemia with a mixed T-cell/B-cell phenotype

We report a case of large granular lymphocytic leukaemia (LGLL) with mixed T-cell/B-cell phenotypes. The LGLL cells expressed T-cell markers such as CD1, CD2, CD3, CD5, CD7, CD8 and CD57. The CD8⁺ LGLL cells coexpressed B-cell markers including CD20 and PCA-1, and a fraction of purified CD8⁺ LGLL cells secreted double isotypes of immunoglobulins (IgG-κ and IgA-κ). Both TCRB and IGH genes were clonally rearranged. The LGLL cells could be divided into at least three subpopulations that were cytogenetically distinct, and all subpopulations involved the 11q23. The expression of both T- and B-cell markers on the LGLL cells suggests the involvement of a putative common lymphoid progenitor in leukaemic transformation.     

Autoimmune-mediated intestinal inflammation-impact and regulation of antigen-specific CD8+ T cells

BACKGROUND & AIMS: Few data exist regarding mechanisms of mucosal CD8+ T-cell reactivity to epithelial-specific antigen. To dissect the immunologic mechanisms underlying CD8+ T-cell dysregulation, reactivity to a self-antigen expressed in intestinal epithelium of mice bearing a major histocompatibility complex class I-restricted T-cell receptor specific for this antigen was studied. In addition, antigen-specific regulatory CD4+ T cells induced in vivo were tested to control these autoreactive CD8+ T cells. METHODS: Transgenic VILLIN-HA mice were mated with CL4-TCR transgenic mice. Alternatively, adoptive transfer of CL4-TCR transgenic CD8+ T cells into VILLIN-HA transgenic mice was performed to mimic spontaneous encounter of neoantigen. Mucosal CD8+ T cells were characterized under different conditions of tolerance, immunopathology, and active immunosuppression. RESULTS: Transgenic CD8+ T cells from VILLIN-HA x CL4-TCR transgenic mice preferentially migrated and expanded in mucosal lymphoid tissues. Although transgenic CD8+ T cells showed signs of T-cell activation, they failed to cause tissue damage. This was accompanied by the induction/expansion of CD4+ and CD8+, Foxp3-expressing T cells. In contrast, adoptive transfer of naive transgenic CD8+ T cells from CL4-TCR transgenic mice into VILLIN-HA transgenic mice induced severe intestinal inflammation with poor clinical course of disease. Transgenic CD8+ T cells secreted vigorous amounts of proinflammatory cytokines like interferon gamma/tumor necrosis factor alpha. Strikingly, this acute wasting disease was significantly ameliorated by cotransfer of antigen-specific regulatory CD4+ T cells. CONCLUSIONS: Epithelial-specific antigen expression is sufficient to trigger severe antigen-specific CD8+ T-cell-mediated intestinal inflammation; this might be controlled by antigen-specific regulatory T cells under physiological conditions.     

Poor lymphocyte recovery following CD34-selected autologous peripheral blood stem cell transplantation for non-Hodgkin's lymphoma

Positive selection of CD34+ cells in autologous grafts, designed to deplete tumour cells, also results in T-cell depletion. To assess the reconstitution of the different lymphocyte subsets and of the T-cell repertoire diversity following autologous transplantation of selected CD34+ peripheral blood stem cells (PBSC), we analysed sequential blood samples in eight patients autografted for advanced B-cell non-Hodgkin's lymphoma in a phase I-II pilot study. Although natural killer cell recovery was rapid, T- and B-cell recovery was delayed with a median of 110/microliters CD4+, 175/microliters CD8+ T cells and 45/microliters B cells at 12 months post-transplant. The naive CD45RA+ T-cell compartment was profoundly deficient up to 12 months for both CD4+ and CD8+ subsets. A transient expansion of memory CD8+CD45RO+ T cells consisting of an increased percentage of CD57+CD28- cells occurred within the first 3 months post-transplant, but the memory CD4+CD45RO+ T cells remained far below the normal value. The CD8+CD28+ T-cell subset did not recover. Using multiplex PCR analysis of the T-cell receptor gamma locus, we found that the repertoire diversity improved at 12 months after being poor and oligoclonal during the first 3 months post-transplant. As shown by monoplex PCRgamma analysis of every VJ combination, despite T-cell depletion of the graft, mature T cells were carried over with the selected CD34+ PBSC and contributed to the T-cell recovery after transplantation.