Cytotoxic T lymphocytes specific for self tumor immunoglobulin express T cell receptor delta chain

γδ T Cells in the Tumor Microenvironment-Interactions With Other Immune Cells

A growing number of studies have shown that γδ T cells play a pivotal role in mediating the clearance of tumors and pathogen-infected cells with their potent cytotoxic, cytolytic, and unique immune-modulating functions. Unlike the more abundant αβ T cells, γδ T cells can recognize a broad range of tumors and infected cells without the requirement of antigen presentation via major histocompatibility complex (MHC) molecules. Our group has recently demonstrated parts of the mechanisms of T-cell receptor (TCR)-dependent activation of Vγ9Vδ2+ T cells by tumors following the presentation of phosphoantigens, intermediates of the mevalonate pathway. This process is mediated through the B7 immunoglobulin family-like butyrophilin 2A1 (BTN2A1) and BTN3A1 complexes. Such recognition results in activation, a robust immunosurveillance process, and elicits rapid γδ T-cell immune responses. These include targeted cell killing, and the ability to produce copious quantities of cytokines and chemokines to exert immune-modulating properties and to interact with other immune cells. This immune cell network includes αβ T cells, B cells, dendritic cells, macrophages, monocytes, natural killer cells, and neutrophils, hence heavily influencing the outcome of immune responses. This key role in orchestrating immune cells and their natural tropism for tumor microenvironment makes γδ T cells an attractive target for cancer immunotherapy. Here, we review the current understanding of these important interactions and highlight the implications of the crosstalk between γδ T cells and other immune cells in the context of anti-tumor immunity.

Ligand recognition by the γδ TCR and discrimination between homeostasis and stress conditions

T lymphocytes comprise cells expressing either an αβ or a γδ TCR. The riddle how αβ TCRs are triggered by specific peptides presented in the context of MHC was elucidated some time ago. In contrast, the mechanisms that underlie antigen recognition by γδ TCRs are still baffling the scientific community. It is clear that activation of γδ TCRs does not necessarily depend on MHC antigen presentation. To date, diverse and largely host-cell-derived molecules have been identified as cognate antigens for the γδ TCR. However, for most γδ TCRs, the activating ligand is still unknown and many open questions with regard to physiological relevance and generalizable concepts remain. Especially the question of how γδ T cells can distinguish homeostatic from stress conditions via their TCR remains largely unresolved. Recent discoveries in the field might have paved the way towards a better understanding of antigen recognition by the γδ TCR and have made it conceivable to revise the current knowledge and contextualize the new findings.

Revisiting the Interaction of γδ T-Cells and B-Cells

Right after the discovery of γδ T-cells in 1984, people started asking how γδ T-cells interact with other immune cells such as B-cells. Early reports showed that γδ T-cells are able to help B-cells to produce antibodies and to sustain the production of germinal centers. Interestingly, the presence of γδ T-cells seems to promote the generation of antibodies against “self” and less against challenging pathogens. More recently, these hypotheses were supported using γδ T-cell-deficient mouse strains, in different mouse models of systemic lupus erythematous, and after induction of epithelial cell damage. Together, these studies suggest that the link between γδ T-cells and the production of autoantibodies may be more relevant for the development of autoimmune diseases than generally acknowledged and thus targeting γδ T-cells could represent a new therapeutic strategy. In this review, we focus on what is known about the communication between γδ T-cells and B-cells, and we discuss the importance of this interaction in the context of autoimmunity.

Dual Face of Vγ9Vδ2-T Cells in Tumor Immunology: Anti- versus Pro-Tumoral Activities

Vγ9Vδ2-T cells are considered as potent effector cells for tumor immunotherapy through directly killing tumor cells and indirectly regulating other innate and adaptive immune cells to establish antitumoral immunity. The antitumoral activity of Vγ9Vδ2-T cells is governed by a complicated set of activating and inhibitory cell receptors. In addition, cytokine milieu in tumor microenvironment can also induce the pro-tumoral activities and functional plasticity of Vγ9Vδ2-T cells. Here, we review the anti- versus pro-tumoral activities of Vγ9Vδ2-T cells and discuss the mechanisms underlying the recognition, activation, differentiation and regulation of Vγ9Vδ2-T cells in tumor immunosurveillance. The comprehensive understanding of the dual face of Vγ9Vδ2-T cells in tumor immunology may improve the therapeutic efficacy and clinical outcomes of Vγ9Vδ2-T cell-based tumor immunotherapy.

Extensive expansion of primary human gamma delta T cells generates cytotoxic effector memory cells that can be labeled with Feraheme for cellular MRI

Gamma delta T cells (GDTc) comprise a small subset of cytolytic T cells shown to kill malignant cells in vitro and in vivo. We have developed a novel protocol to expand GDTc from human blood whereby GDTc were initially expanded in the presence of alpha beta T cells (ABTc) that were then depleted prior to use. We achieved clinically relevant expansions of up to 18,485-fold total GDTc, with 18,849-fold expansion of the Vδ1 GDTc subset over 21 days. ABTc depletion yielded 88.1 ± 4.2 % GDTc purity, and GDTc continued to expand after separation. Immunophenotyping revealed that expanded GDTc were mostly CD27-CD45RA- and CD27-CD45RA+ effector memory cells. GDTc cytotoxicity against PC-3M prostate cancer, U87 glioblastoma and EM-2 leukemia cells was confirmed. Both expanded Vδ1 and Vδ2 GDTc were cytotoxic to PC-3M in a T cell antigen receptor- and CD18-dependent manner. We are the first to label GDTc with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles for cellular MRI. Using protamine sulfate and magnetofection, we achieved up to 40 % labeling with clinically approved Feraheme (Ferumoxytol), as determined by enumeration of Perls' Prussian blue-stained cytospins. Electron microscopy at 2,800× magnification verified the presence of internalized clusters of iron oxide; however, high iron uptake correlated negatively with cell viability. We found improved USPIO uptake later in culture. MRI of GDTc in agarose phantoms was performed at 3 Tesla. The signal-to-noise ratios for unlabeled and labeled cells were 56 and 21, respectively. Thus, Feraheme-labeled GDTc could be readily detected in vitro via MRI.

Diversity of γδ T-cell antigens

In the last two decades, it has become clear that γδ T cells recognize a diverse array of antigens including self and foreign, large and small, and peptidic and non-peptidic molecules. In this respect, γδ antigens as a whole resemble more the antigens recognized by antibodies than those recognized by αβ T cells. Because of this antigenic diversity, no single mechanism-such as the major histocompatibility complex (MHC) restriction of αβ T cells-is likely to provide a basis for all observed T-cell antigen receptor (TCR)-dependent γδ T-cell responses. Furthermore, available evidence suggests that many individual γδ T cells are poly-specific, probably using different modes of ligand recognition in their responses to unrelated antigens. While posing a unique challenge in the maintenance of self-tolerance, this broad reactivity pattern might enable multiple overlapping uses of γδ T-cell populations, and thus generate a more efficient immune response.

Close link between development and function of gamma-delta T cells

Murine γδ T cells develop as the first T-cell lineage within the fetal thymus and disproportionately localize in mucosal tissues such as lung, skin, uterus, and intestine of adult mice. These unique developmental features and distribution patterns of γδ T cells enable rapid functioning against various insults from pathogens. γδ T cells are also able to respond to local inflammation and consequently regulate the pathogenesis of autoimmune disorders and development of tumors in mice and humans. Hence, it is clinically important to understand the mechanisms that regulate γδ T cell functions. Recent evidence has shown that generations of effector γδ T cell subsets producing IFN-γ, IL-4, and IL-17 are programmed in the murine thymus before their migration to peripheral tissues. This review outlines our current understanding of the development and function of γδ T cells as they influence both innate and acquired immunity.

Evaluation of Epstein-Barr virus latent membrane protein 2 specific T-cell receptors driven by T-cell specific promoters using lentiviral vector

Transduction of latent membrane protein 2 (LMP2)-specific T-cell receptors into activated T lymphocytes may provide a universal, MHC-restricted mean to treat EBV-associated tumors in adoptive immunotherapy. We compared TCR-specific promoters of distinct origin in lentiviral vectors, that is, Vβ6.7, delta, luria, and Vβ5.1 to evaluate TCR gene expression in human primary peripheral blood monocytes and T cell line HSB2. Vectors containing Vβ 6.7 promoter were found to be optimal for expression in PBMCs, and they maintained expression of the transduced TCRs for up to 7 weeks. These cells had the potential to recognize subdominant EBV latency antigens as measured by cytotoxicity and IFN-γ secretion. The nude mice also exhibited significant resistance to the HLA-A2 and LMP2-positive CNE tumor cell challenge after being infused with lentiviral transduced CTLs. In conclusion, LMP2-specific CTLs by lentiviral transduction have the potential use for treatment of EBV-related tumors.

Peptide antigens for gamma/delta T cells

γδ T cells express adaptive antigen receptors encoded by rearranging genes. Their diversity is highest in the small region of TCR V-J junctions, especially in the δ chain, which should enable the γδ TCRs to distinguish differences in small epitopes. Indeed, recognition of small molecules, and of an epitope on a larger protein has been reported. Responses to small non-peptides known as phospho-antigens are multi-clonal yet limited to a single γδ T cell subset in humans and non-human primates. Responses to small peptides are multi-clonal or oligo-clonal, include more than one subset of γδ T cells, and occur in rodents and primates. However, less effort has been devoted to investigate the peptide responses. To settle the questions of whether peptides can be ligands for the γδ TCRs, and whether responses to small peptides might occur normally, peptide binding will have to be demonstrated, and natural peptide ligands identified.

Human Vδ1 γδ T cells expanded from peripheral blood exhibit specific cytotoxicity against B-cell chronic lymphocytic leukemia-derived cells

BACKGROUND AIMS

There is increasing interest in using γδ T cells (GDTC) for cancer immunotherapy. Most studies have been concerned with the Vδ2 subset in blood, for which several expansion protocols exist. We have developed a protocol to expand Vδ1 and Vδ2 preferentially from human blood. We have characterized these subsets and their specificities for leukemic targets.

METHODS

GDTC were isolated from the peripheral blood mononuclear cells (PBMC) of healthy donors via positive magnetic cell sorting; their proliferation in vitro was induced by exposure to the mitogen concanavalin A (Con A). CD107 and cytotoxicity (Cr(51)-release and flow cytometric) assays were performed. GDTC clones and target cells were immunophenotyped via flow cytometry.

RESULTS

Longer initial exposure to Con A typically resulted in higher Vδ1 prevalence. Vδ1 were activated by and cytotoxic to B-cell chronic lymphocytic leukemia (B-CLL)-derived MEC1 cells, whereas Vδ2 also responded to MEC1 but more so to the Philadelphia chromosome-positive [Ph+] leukemia cell line EM-enhanced green fluorescent protein (2eGFPluc). Vδ2 clone cytotoxicity against EM-2eGFPluc correlated with Vδ2 T-cell antigen receptor (TCR) and receptor found on Natural Killer cells and many T-cells (NKG2D), whereas Vδ1 clone cytotoxicity versus MEC1 correlated with Vδ1 TCR, CD56 and CD95 expression. Vδ1 also killed Epstein-Barr Virus (EBV)-negative B-CLL-derived TMD2 cells. Immunophenotyping revealed reduced HLA-ABC expression on EM-2eGFPluc, whereas MEC1 and TMD2 exhibited higher Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAILR1).

CONCLUSIONS

Our ability to expand peripheral Vδ1 cells and show their cytotoxicity to B-CLL-derived cell lines suggests that this novel approach to the cellular treatment of B-CLL may be feasible.

Anti-leukemia activity of in vitro-expanded human gamma delta T cells in a xenogeneic Ph+ leukemia model

Gamma delta T cells (GDTc) lyse a variety of hematological and solid tumour cells in vitro and in vivo, and are thus promising candidates for cellular immunotherapy. We have developed a protocol to expand human GDTc in vitro, yielding highly cytotoxic Vgamma9/Vdelta2 CD27/CD45RA double negative effector memory cells. These cells express CD16, CD45RO, CD56, CD95 and NKG2D. Flow cytometric, clonogenic, and chromium release assays confirmed their specific cytotoxicity against Ph(+) cell lines in vitro. We have generated a fluorescent and bioluminescent Ph(+) cell line, EM-2eGFPluc, and established a novel xenogeneic leukemia model. Intravenous injection of EM-2eGFPluc into NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice resulted in significant dose-dependent bone marrow engraftment; lower levels engrafted in blood, lung, liver and spleen. In vitro-expanded human GDTc injected intraperitoneally were found at higher levels in blood and organs compared to those injected intravenously; GDTc survived at least 33 days post-injection. In therapy experiments, we documented decreased bone marrow leukemia burden in mice treated with GDTc. Live GDTc were found in spleen and bone marrow at endpoint, suggesting the potential usefulness of this therapy.

Activation of gamma delta T cells by Borrelia burgdorferi is indirect via a TLR- and caspase-dependent pathway

Activation of the innate immune system typically precedes engagement of adaptive immunity. Cells at the interface between these two arms of the immune response are thus critical to provide full engagement of host defense. Among the innate T cells at this interface are gammadelta T cells. gammadelta T cells contribute to the defense from a variety of infectious organisms, yet little is understood regarding how they are activated. We have previously observed that human gammadelta T cells of the Vdelta1 subset accumulate in inflamed joints in Lyme arthritis and proliferate in response to stimulation with the causative spirochete, Borrelia burgdorferi. We now observe that murine gammadelta T cells are also activated by B. burgdorferi and that in both cases the activation is indirect via TLR stimulation on dendritic cells or monocytes. Furthermore, B. burgdorferi stimulation of monocytes via TLR, and secondary activation of gammadelta T cells, are both caspase-dependent.

An autonomous CDR3delta is sufficient for recognition of the nonclassical MHC class I molecules T10 and T22 by gammadelta T cells

It remains unclear whether gammadelta T cell antigen receptors (TCRs) detect antigens in a way similar to antibodies or alphabeta TCRs. Here we show that reactivity between the G8 and KN6 gammadelta TCRs and the major histocompatibility complex class Ib molecule T22 could be recapitulated, with retention of wild-type ligand affinity, in an alphabeta TCR after grafting of a G8 or KN6 complementarity-determining region 3-delta (CDR3delta) loop in place of the CDR3alpha loop of an alphabeta TCR. We also found that a shared sequence motif in CDR3delta loops of all T22-reactive gammadelta TCRs bound T22 in energetically distinct ways, and that T10(d), which bound G8 with weak affinity, was converted into a high-affinity ligand by a single point mutation. Our results demonstrate unprecedented autonomy of a single CDR3 loop in antigen recognition.

Characterization of the gammadelta T cell response to acute leukemia

BACKGROUND

Previous work from our center has suggested a correlation between increased donor-derived Vdelta1+ gammadelta T cells and long-term relapse-free survival following bone marrow transplantation for leukemia. Questions remain, however, as to whether this observation can be explained by a gammadelta T cell-based immune response against primary leukemia.

METHODS

We examined gammadelta T cell receptor (TCR) phenotype, cell proliferation, and cytolytic activity following culture with irradiated primary leukemia blasts from a haploidentical first-degree relative. Subsequently, we also studied the gammadelta TCR phenotype and complimentarity determining region 3 (CDR3) cDNA sequences from 17 newly diagnosed leukemia patients.

RESULTS

In 17/28 (61%) of in vitro cultures, gammadelta T cells proliferated in culture with primary blasts. Vdelta1+ T cells were proportionally increased in all cultures and were the predominant cell population in 6/17. In the 7 cultures where cytotoxicity could be assessed, 6 (86%) showed some degree of cytotoxicity to the primary leukemia. Vdelta1+ T cells were also the predominant gammadelta T cell subtype in pre-treatment leukemia patients principally due to loss of Vdelta2+ T cells rather than expansion of Vdelta1+ cells. The Vdelta1 CDR3-region cDNA sequence from these patients revealed exclusive use of the Jdelta1 constant region and sequence conservation in 4/11 patients.

CONCLUSIONS

gammadelta T cells exhibit an in vitro response to primary leukemia blasts that is manifested by proliferation, an increased proportion of Vdelta1+ T cells, and cytotoxicity to the primary leukemia blasts. The Vdelta1+ T cell population is also predominant in newly diagnosed leukemia patients likely due to a loss of circulating Vdelta2+ T cells. A small proportion of newly diagnosed patients showed Vdelta1 CDR3 region similarity. These findings suggest a role for gammadelta T cells in the immune response to leukemia.

gammadelta T cells: a new frontier for immunotherapy?

The use of cytolytic effector cells as therapy for malignant disease has been a central focus of basic and clinical research for nearly 2 decades. Since the original descriptions of in vitro lymphocyte-mediated cytotoxicity against human tumor cells, there have been numerous attempts to exploit such observations for therapeutic use, with decidedly mixed results. Most studies have focused on the role of either natural killer cells or cytotoxic CD8 + alphabeta T cells as the primary mediators of antitumor cytotoxicity, and until recently little attention has been paid to the role of gammadelta T cells in this capacity. This is partially due to a lack of understanding of the mechanisms of gammadelta T-cell immune responses to tumors, as well as the practical problem of obtaining a sufficient number of gammadelta T cells for clinical-scale administration. In this article, we discuss the biological and clinical rationale for developing gammadelta T cell-based immunotherapies for the treatment of a variety of malignant conditions. It is our view that infusing supraphysiological numbers of tumor-reactive gammadelta T cells-either in the autologous or allogeneic setting-might be used to restore or augment innate immune responses against malignancies. Accordingly, we will also discuss how we and others are working to overcome some of the practical limitations that have so far limited the direct clinical delivery of highly purified human gammadelta T cells for the treatment of both hematologic and solid tumors.

Perturbation and proinflammatory type activation of V delta 1(+) gamma delta T cells in African children with Plasmodium falciparum malaria

gamma delta T cells have variously been implicated in the protection against, and the pathogenesis of, malaria, but few studies have examined the gamma delta T-cell response to malaria in African children, who suffer the large majority of malaria-associated morbidity and mortality. This is unfortunate, since available data suggest that simple extrapolation of conclusions drawn from studies of nonimmune adults ex vivo and in vitro is not always possible. Here we show that both the frequencies and the absolute numbers of gamma delta T cells are transiently increased following treatment of Plasmodium falciparum malaria in Ghanaian children and they can constitute 30 to 50% of all T cells shortly after initiation of antimalarial chemotherapy. The bulk of the gamma delta T cells involved in this perturbation expressed V delta 1 and had a highly activated phenotype. Analysis of the T-cell receptors (TCR) of the V delta 1(+) cell population at the peak of their increase showed that all expressed V gamma chains were used, and CDR3 length polymorphism indicated that the expanded V delta 1 population was highly polyclonal. A very high proportion of the V delta 1(+) T cells produced gamma interferon, while fewer V delta 1(+) cells than the average proportion of all CD3(+) cells produced tumor necrosis factor alpha. No interleukin 10 production was detected among TCR-gamma delta(+) cells in general or V delta 1(+) cells in particular. Taken together, our data point to an immunoregulatory role of the expanded V delta 1(+) T-cell population in this group of semi-immune P. falciparum malaria patients.

Anti-tumor effects of human peripheral gammadelta T cells in a mouse tumor model

Peripheral gammadelta T cells derived from healthy donors were found to exhibit cytotoxicity against a variety of tumor cell lines in vitro, including CNE2, which was established from nasopharyngeal carcinoma (NPC). The anti-tumor effects were further studied in a mouse model. Control nude mice inoculated s.c. with 5 x 10(6) CNE2 cells regularly developed hypodermal tumors, which progressively increased in size, and animals had a mean survival of 35 +/- 3.4 days. Tumor growth was arrested and tumor size was reduced after animals were infused with 5 x 10(7) gammadelta T cells derived from a healthy donor. The anti-tumor effects were temporary, however, and tumor growth was resumed after about 1 week in a group of the animals that had been given a single dose of gammadelta T cells. In another group of animals given 2 doses of gammadelta cells 1 week apart, resumption of tumor growth was delayed for a further week. Mean survival of the 2 groups was increased to 61 +/- 15.7 and 74 +/- 12.9 days, respectively. Immunohistology revealed an accumulation of infused cells in tumors attended by focal tumor necrosis in specimens taken 2 days after infusion. Infiltrative cells virtually disappeared from tumor tissues 6 days after infusion, accompanied by increased mitotic indices of tumor cells. These temporal relationships suggested that the accumulation of infused gammadelta T cells in hypodermal tumors was responsible for the observed anti-tumor effects.

Circulating and tumor-infiltrating gamma delta T Cells in patients with B-cell lymphomas

In order to analyze the involvement of gamma delta T cells in the immune surveillance against B cell lymphomas (BCL), we investigated the proportion of circulating gamma delta T cells in 52 BCL patients using two-color flow cytometry, together with tumor-infiltrating gamma delta T cells in 22 of those patients. We found that the proportion of tumor-infiltrating gamma delta T cells in BCL patients was not different from that of lymph node gamma delta T cells in reactive hyperplasia patients. However, a decreased percentage of circulating gamma delta T cells were observed in indolent lymphoma (IL) and limited aggressive lymphoma (AL) patients when compared with normal controls. In contrast, as a result of a histogram, advanced AL patients were divided into two subgroups: the patients with increased circulating gamma delta T cells and those without any increase. However, there was no difference in the clinical features of between the two AL subgroups.

Stimulation of γδ T cells by aminobisphosphonates and induction of antiplasma cell activity in multiple myeloma

Bisphosphonates are well-known inhibitors of osteoclastic bone resorption, but recent clinical reports support the possibility of direct or indirect antitumor effects by these compounds. Because bisphosphonates share structural homologies with recently identified γδ T-cell ligands, we examined the stimulatory capacity of bisphosphonates to γδ T cells and determined whether γδ T-cell stimulation by bisphosphonates could be exploited to generate antiplasma cell activity in multiple myeloma (MM). All tested aminobisphosphonates (alendronate, ibandronate, and pamidronate) induced significant expansion of γδ T cells (Vγ9Vδ2 subset) in peripheral blood mononuclear cell cultures of healthy donors at clinically relevant concentrations (half-maximal activity, 0.9-4 μmol/L). The proliferative response of γδ T cells to aminobisphosphonates was IL-2 dependent, whereas activation of γδ T cells (up-regulation of CD25 and CD69) occurred in the absence of exogenous cytokines. Pamidronate-activated γδ T cells produced cytokines (ie, interferon [IFN]-γ) and exhibited specific cytotoxicity against lymphoma (Daudi) and myeloma cell lines (RPMI 8226, U266). Pamidronate-treated bone marrow (BM) cultures of 24 patients with MM showed significantly reduced plasma cell survival compared with untreated cultures, especially in cultures in which activation of BM-γδ T cells was evident (14 of 24 patients with MM). γδ T-cell depletion from BM cultures completely abrogated the cytoreductive effect on myeloma cells in 2 of 3 tested patients with MM. These results show that aminobisphosphonates stimulating γδ T cells have pronounced effects on the immune system, which might contribute to the antitumor effects of these drugs.

Stimulation of γδ T cells by aminobisphosphonates and induction of antiplasma cell activity in multiple myeloma

Bisphosphonates are well-known inhibitors of osteoclastic bone resorption, but recent clinical reports support the possibility of direct or indirect antitumor effects by these compounds. Because bisphosphonates share structural homologies with recently identified γδ T-cell ligands, we examined the stimulatory capacity of bisphosphonates to γδ T cells and determined whether γδ T-cell stimulation by bisphosphonates could be exploited to generate antiplasma cell activity in multiple myeloma (MM). All tested aminobisphosphonates (alendronate, ibandronate, and pamidronate) induced significant expansion of γδ T cells (Vγ9Vδ2 subset) in peripheral blood mononuclear cell cultures of healthy donors at clinically relevant concentrations (half-maximal activity, 0.9-4 μmol/L). The proliferative response of γδ T cells to aminobisphosphonates was IL-2 dependent, whereas activation of γδ T cells (up-regulation of CD25 and CD69) occurred in the absence of exogenous cytokines. Pamidronate-activated γδ T cells produced cytokines (ie, interferon [IFN]-γ) and exhibited specific cytotoxicity against lymphoma (Daudi) and myeloma cell lines (RPMI 8226, U266). Pamidronate-treated bone marrow (BM) cultures of 24 patients with MM showed significantly reduced plasma cell survival compared with untreated cultures, especially in cultures in which activation of BM-γδ T cells was evident (14 of 24 patients with MM). γδ T-cell depletion from BM cultures completely abrogated the cytoreductive effect on myeloma cells in 2 of 3 tested patients with MM. These results show that aminobisphosphonates stimulating γδ T cells have pronounced effects on the immune system, which might contribute to the antitumor effects of these drugs.

The expansion of human gammadelta T cells in response to Daudi cells requires the participation of CD4+ T cells

The Burkitt's lymphoma cell line Daudi is a potent inducer of human gammadelta T-cell expansion. Using an in vitro culture system comprised of irradiated Daudi cells as stimulators and normal human lymphocytes as responders, the cellular determinants of this response were investigated. Three of four monoclonal antibodies (mAbs 1-1C4, L243, and 9.3F10) directed against disparate epitopes of human major histocompatibility complex (MHC) class II, as well as a mAb with specificity for CD4 (OKT4), inhibited the expansion of gammadelta T cells in response to Daudi cell stimulators. mAbs with a specificity for CD74 and CD8 were non-inhibitory. Lymphocyte depletion experiments demonstrated a critical role for the CD4+ T-cell subset in the expansion of gammadelta T cells. Other data pointed towards requirements for direct cell contact in this system, and the addition of exogenous recombinant interleukin (IL)-2, IL-4, and IL-12 failed to reconstitute gammadelta T-cell expansion in CD4+ lymphocyte-depleted cultures. These results complement previous findings in murine infectious disease and mycobacterial systems, providing a direct demonstration that CD4+ T cells play a role in gammadelta T-cell expansion through an interaction with human leucocyte antigen (HLA) class II on Daudi cells. The data point towards important functional links between the acquired and natural immune systems.

A human natural antibody to adenocarcinoma that inhibits tumour cell migration

We characterized a natural human antibody to adenocarcinomas and investigated the biological role of this Ab/Ag complex in cancer expansion. Human monoclonal antibodies (HuMAbs) were generated with hybridoma fusion methods using regional nodal lymphocytes of colon carcinoma patients. Among 1036 HuMAbs, only one, termed SK1, an IgM, was adenocarcinoma specific in the immunohistochemical study. The antigen recognized by SK1 (Ag-SK1) was a glycoprotein with a molecular weight of 42-46 kDa. The expression of Ag-SK1 on carcinoma cells varied according to the cell growth periods but was independent of cell cycle state as elucidated by two-colour fluorescence-activated cell sorter (FACS) analysis. A dot-blot analysis showed that the concentration of Ag-SK1 per total protein differed considerably among eight colon carcinoma cells examined and that the difference was closely correlated with the invasion capacity of the cells as assessed by a microchemotaxis assay. Furthermore, up to 87% of cell migration was inhibited by SK1 in a dose-dependent manner. These data suggested that Ag-SK1 is metabolized and expressed on highly invasive carcinoma cells. In addition, it appears that, although rare, some patients do mount an anti-cancer antigen response in their draining lymph nodes. A HuMAb such as SK1 may be a good candidate for the treatment of cancer invasion and metastasis.

Heat shock proteins and the antitumor T cell response

Heat shock proteins (HSP) have been shown to participate in the antitumor T cell response. First, HSP play a crucial role in the intracellular pathway for antigen processing where HSP can make complexes with a broad spectrum of cellular proteins and peptides through their chaperone functions. In this pathway, macrophages are required for processing the chaperoned peptides to make stable molecules with the major histocompatibility complex (MHC) class I molecules, even when HSP-peptide complexes are exogenously administered. Through this pathway, vaccination with HSP-peptide complexes is thus able to elicit the response of CD8+ T cells specific for the chaperoned peptides. These findings suggest an essential role of HSP in 'cross-priming' and their usefulness for antitumor vaccination with tumor peptides. Second, HSP have been suggested to be expressed on the cell surface by transformation and, in addition, to function as antigen-presenting molecules for double negative T cells. Third, HSP derived from tumor cells have reportedly been recognized by T cells with either T cell receptor (TCR)-alphabeta or TCR-gammadelta. These lines of evidence therefore indicate that HSP may be potentially promising target molecules for antitumor T cell immunotherapy.

Intercellular and Intracellular Events Following the MHC-Unrestricted TCR Recognition of a Tumor-Specific Peptide Epitope on the Epithelial Antigen MUC1

We examined the functional and molecular parameters involved in direct TCR recognition of a tumor-specific peptide epitope on the tumor Ag MUC1. This peptide epitope is tandemly repeated and recognized on the native molecule rather than processed and bound to the MHC. Even though the TCR was not MHC restricted, intercellular interactions found to facilitate this recognition included intercellular adhesion molecule-1/LFA-1, LFA-3/CD2, and class I/CD8. Intracellular parameters of MHC-unrestricted CTL activation were examined to compare the recognition of the MUC1 epitope presented on synthetic microspheres, with the recognition of the native epitope in the context of other molecules on the target cells. The epitope on microspheres induced a transient influx of Ca2+ that was not accompanied by detectable tyrosine phosphorylation of the ζ-associated protein ZAP-70, whereas recognition of MUC1 epitopes on tumor cells caused a sustained Ca2+ influx and ZAP-70 phosphorylation. The transient influx of Ca2+ was not sufficient to cause translocation of the nuclear factor of activated T cells (NF-AT) into the nucleus or CTL proliferation. In contrast, recognition of the MUC1 epitope on tumor cells resulted in full activation of the CTL, nuclear translocation of NF-AT, and proliferation. MHC-unrestricted TCR triggering, therefore, involves similar intercellular and intracellular events that participate in the conventional, MHC-restricted Ag recognition. Direct recognition of the MUC1 peptide epitope by the TCR in the absence of presentation by the MHC induces a partial signal that is completed by further interactions of other receptor/ligand pairs on the surface of the CTL and their target cells.

Vaccine strategies in non-Hodgkin's lymphomas

As described above, the most recent advances in anti-idiotype vaccination strategies have gone hand in hand with recent developments in molecular biology and other forms of cancer therapy. The techniques that are currently available in antibody engineering will greatly facilitate protein production and purification and will reduce the time and effort needed to produce the patient specific vaccines. Cytokine (gene) therapy has extensively been studied in cancer treatment and cancer vaccination and some therapeutic strategies are currently being evaluated in clinical trials (Bubenik, 1996). Combination therapy of idiotypic vaccination with cytokine therapy has recently been explored with promising results. The main focus so far has been on GM-CSF and IL-2, although other cytokines might prove to be efficient in stimulating different effector arms of the immune system. The nature of the immune response mounted by the host against the tumour and the mechanisms by which the tumour cells escape the effector functions of the immune system are not yet fully known. A better knowledge of the nature of B-cell lymphomas and the relation to the patient's immune system will therefore benefit the further development of the therapeutic strategies. Further research will provide us with a better view of how to break the immune tolerance and of which components of the immune system have to be targeted in order to obtain optimal therapeutic results.

Apoptosis of Fashigh CD4+ synovial T cells by borrelia-reactive Fas-ligand(high) gamma delta T cells in Lyme arthritis

The function of the minor subset of T lymphocytes bearing the gamma delta T cell antigen receptor is uncertain. Although some gamma delta T cells react to microbial products, responsiveness has only rarely been demonstrated toward a bacterial antigen from a naturally occurring human infection. Synovial fluid lymphocytes from patients with Lyme arthritis contain a large proportion of gamma delta cells that proliferate in response to the causative spirochete, Borrelia burgdorferi. Furthermore, synovial gamma delta T cell clones express elevated and sustained levels of the ligand for Fas (APO-1, CD95) compared to alpha beta T cells, and induce apoptosis of Fashigh CD4+ synovial lymphocytes. The findings suggest that gamma delta T cells contribute to defense in human infections, as well as manifest an immunoregulatory function at inflammatory sites by a Fas-dependent process.

Gamma delta T cell help of B cells is induced by repeated parasitic infection, in the absence of other T cells

BACKGROUND

gamma delta T cells, like alpha beta T cells, are components of all well-studied vertebrate immune systems. Yet, the contribution of gamma delta T cells to immune responses is poorly characterized. In particular, it has not been resolved whether gamma delta cells, independent of any other T cells, can help B cells produce immunoglobulin and form germinal centers, anatomical foci of specialized T cell-B cell collaboration.

RESULTS

TCR beta-/- mice, which lack all T cells except gamma delta T cells, routinely displayed higher levels of antibody than fully T cell-deficient mice. Repeated parasitic infection of TCR beta-/- mice, but not of T cell-deficient mice, increased antibody levels and induced germinal centers that contained B cells and monoclonal gamma delta cells in close juxtaposition. However, antibody specificities were more commonly against self than against the challenging pathogen. gamma delta T cell-B cell help was not induced by repeated inoculation of TCR beta-/- mice with mycobacterial antigens.

CONCLUSIONS

In the absence of any other T cells, gamma delta T cell-B cell collaboration can be significantly enhanced by repeated infection. However, the lack of obvious enrichment for antibodies against the challenging pathogen distinguishes gamma delta T cell help from alpha beta T cell help induced under analogous circumstances. The increased production of generalized antibodies may be particularly relevant to the development of autoimmunity, which commonly occurs in patients suffering from alpha beta T cell deficiencies, such as AIDS.

Isolation and characterisation of T lymphocytes from sural nerve biopsies in patients with Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy

OBJECTIVES

To characterise cultured T lymphocytes from nerve biopsies in patients with Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP).

METHODS

Sural nerve biopsies, obtained from six patients with Guillain-Barré syndrome, four with CIDP, and six controls with other neuropathies, were cultured with 20 U/ml recombinant interleukin-2 (IL-2) for eight weeks. Flow cytometry was used to determine the phenotype of cultured T lymphocytes. Their proliferative responses to a range of bacterial antigens were also examined.

RESULTS

T cell lines were established from four of six patients with Guillain-Barré syndrome, one of four with CIDP, one patient with peripheral nerve vasculitis, and none of five controls with non-inflammatory neuropathies. One of these T cell lines from a patient with Guillain-Barré syndrome, preceded by Campylobacter jejuni infection, consisted entirely of gamma delta TCR+ T lymphocytes. The peripheral blood of this patient also contained an increased frequency of gamma delta T cells when stimulated with C jejuni. The nerve derived T cell lines failed to show a proliferative response to bacterial antigens or to a preparation of myelin proteins.

CONCLUSIONS

A new technique to isolate T cells from nerve biopsies in patients with Guillain-Barré syndrome and CIDP is reported. This technique may prove to be a useful tool in the investigation of the pathogenesis of other inflammatory neuropathies such as peripheral nerve vasculitis. The isolation of a gamma delta TCR+ nerve T cell line is of interest because of the possibility that these cells might respond to glycolipid epitopes common to C jejuni and peripheral nerve gangliosides.

Cytotoxic T lymphocyte recognition of non-Hodgkin's B cell lymphomas

Human cytolytic T lymphocytes specific for autologous Burkitt's lymphoma express the gamma, delta T cell receptor and recognize immunoglobulin idiotype in an MHC-unrestricted manner. Antibodies against a member of the heat shock protein 70 family inhibit this specific cytotoxicity, implicating these molecules in tumor recognition and antigen presentation. Such data is relevant to the design of novel immunotherapies for cancer and provides new insights into target recognition by gamma, delta T cells.

Germinal center formation, immunoglobulin class switching, and autoantibody production driven by "non alpha/beta" T cells

The production of class-switched antibodies, particularly immunoglobulin (Ig) G1 and IgE, occurs efficiently in T cell receptor (TCR) alpha-/- mice that are congenitally devoid of alpha/beta T cells. This finding runs counter to a wealth of data indicating that IgG1 and IgE synthesis are largely dependent on the collaboration between B and alpha/beta T cells. Furthermore, many of the antibodies synthesized in TCR alpha-/- mice are reactive to a similar spectrum of self-antigens as that targeted by autoantibodies characterizing human systemic lupus erythematosus (SLE). SLE, too, is most commonly regarded as an alpha/beta T cell-mediated condition. To distinguish whether the development of autoantibodies in TCR alpha-/- mice is due to an intrinsic de-regulation of B cells, or to a heretofore poorly characterized collaboration between B and "non-alpha/beta T" cells, the phenotype has been reconstituted by transfer of various populations of B and non-alpha/beta T cells including cloned gamma/delta T cells derived from TCR alpha-/- mice, to severe combined immunodeficient (SCID) mice. The results establish that the reproducible production of IgG1 (including autoantibodies) is a product of non-alpha/beta T cell help that can be provided by gamma/delta T cells. This type of B-T collaboration sustains the production of germinal centers, lymphoid follicles that ordinarily are anatomical signatures of alpha/beta T-B cell collaboration. Thus, non-alpha/beta T cell help may drive Ig synthesis and autoreactivity under various circumstances, especially in cases of alpha/beta T cell immunodeficiency.

Kinetics of transcription factors regulating the RANTES chemokine gene reveal a developmental switch in nuclear events during T-lymphocyte maturation

RANTES is a chemoattractant cytokine (chemokine) whose gene is expressed immediately after stimulation of several cell types but upregulated late (3 to 5 days) after activation in normal T lymphocytes. Here we describe two cis-acting elements in the human RANTES promoter that act in T lymphocytes. One site interacts with NFIL6, which is activated within the first 24 h after T-cell activation. The second site binds an apparently novel complex that is upregulated later, between days 3 and 5. These data provide an explanation for the immediate-early expression of RANTES in some cell types and identify apparently novel factors contributing to late RANTES transcription in T cells. The results reveal a developmental switch occurring during normal T-cell maturation coincident with the onset of terminal differentiation and the binding of late-acting factors to sequences of the RANTES promoter.

Ontogenic development and tissue distribution of V gamma 1-expressing gamma/delta T lymphocytes in normal mice

A hamster monoclonal antibody (mAb) recognizing an epitope in the V gamma 1-J gamma 4-C gamma 4 chain of the gamma/delta T cell receptor has been generated. Using this mAb, we have quantitated the occurrence of V gamma 1-bearing gamma/delta T cells in the developing thymus and in the lymphoid organs and several epithelia of adult mice. The V gamma 1-expressing cells constitute a minor gamma/delta T cell subpopulation during fetal and early postnatal life, but they constitute a major population of gamma/delta T cells in the thymus and in the peripheral lymphoid organs in adult mice. In addition, we found that V gamma 1-bearing cells comprise a large proportion (15-60%) of the gamma/delta T cells present in the intestinal epithelium (i-IEL) in all strains of mice tested. V gamma 1+ i-IEL are present in athymic (nude) mice and in antigen-free mice, demonstrating that they can develop extrathymically and that their presence in the intestinal epithelium is independent of the antigenic load of the gut. Our results show that V gamma 1-bearing lymphocytes account for the largest population of gamma/delta T cells in the mouse. This population includes a thymus-dependent component that homes to the secondary lymphoid organs and a thymus-independent component that constitutes a major fraction of the gamma/delta i-IELs.

Naive CD4+ T cells confer idiotype-specific tumor resistance in the absence of antibodies

CD4+ T cells can recognize a processed idiotypic peptide derived from the mouse lambda 2(315) immunoglobulin light chain. The idiotypic peptide is presented on the I-E(d) class II major histocompatibility complex molecule. Mice made transgenic for a lambda 2(315)-specific alpha beta T cell receptor have been demonstrated to be specifically resistant against a tumor challenge with the MOPC315 (alpha,lambda 2(315)) plasmacytoma (Lauritzsen, G. F., Weiss, S., Dembic, Z. and Bogen, B., Proc. Natl. Acad. Sci. USA 1994, 91: 5700). That study, however, did not rule out a role of either anti-Id antibodies or T cells expressing nontransgenic specificities due to expression of endogenous T cell receptor (TcR) alpha chains. Also, the role of different T cell subsets in protection was unclear. To remove these ambiguities, we have now made the transgenic mice homozygous for the scid mutation, known to inhibit both Ig and TcR gene rearrangements. Such transgenic SCID mice lack B cells and antibodies while they still have plenty of CD4+ and CD4-8- cells expressing the transgenic alpha beta T cell receptor. The number of CD8+ T cell is dramatically reduced. Even so, transgenic SCID mice are protected against a challenge with MOPC315 plasmacytoma cells. Therefore, B cells, as well as novel T cell receptor specificities created by rearrangements of endogenous alpha-chain genes, are both dispensable for effective immunosurveillance in our system. Surprisingly, we found that transgenic CD8+ and CD4-8- cells are idiotype-specific and I-E(d) restricted. However, these T cell subsets are not required for resistance because adoptive transfer experiments demonstrated that highly purified transgenic SCID CD4+ cells suffice for tumor protection.

Responses to T cell receptor/CD3 and interleukin-2 receptor stimulation are altered in T cells from B cell non-Hodgkin's lymphomas

T cells infiltrating (T-TIL) B cell non-Hodgkin's lymphomas (NHL) are thought to represent a local host response to the tumor. However, tumor progression in the presence of this T cell infiltrate suggests that the T-TIL may be functionally impaired. To address this issue we determined whether response to stimulation of T-TIL from 25 patients with NHL through the T cell receptor (TCR/CD3) and the interleukin-2 (IL-2) receptor (IL-2R) was intact, since activation of these receptors is important for proliferation and cytokine production. Our results demonstrate defects in response to stimulation via TCR/CD3 and the IL-2R in T-TIL cells from patients with NHL that were not observed with T cells from the peripheral blood. T-TIL showed minimal proliferation to anti-CD3 and only modest proliferation to IL-2 alone or when combined with anti-CD3. Moreover, cytokine production in T-TIL was impaired since stimulation through the TCR/CD3 complex did not induce mRNA for interferon gamma (IFN gamma), IL-2, IL-4 or IL-10. The functional unresponsiveness of these cells may be linked to altered signalling through the TCR/CD3 since an abnormal tyrosine phosphorylation pattern was detected in T-TIL after stimulation with anti-CD3.

Autotumour reactive T-cell clones among tumour-infiltrating T lymphocytes in B-cell non-Hodgkin's lymphomas

Seventy-three T-cell clones (TCC) were established from tumour-infiltrating lymphocytes-T (TIL-T) derived from lymph nodes involved by B-cell non-Hodgkin's lymphomas (B-NHL) in nine patients with different histological subtypes and clinical stages. 40 TCC (55%) expressed the CD25 Ag and were also able to proliferate in the presence of irradiated autologous B-NHL cells. Among them, 23 autotumour (AuTu) proliferative TCC were found not to proliferate to autologous EBV-transformed B-cell lines, indicating that the proliferative reactivity of these TCC was preferentially directed at autologous B-NHL cells. Tested against autologous B-NHL cells, only three AuTu proliferative TCC (CD8+) showed a significant level of cytotoxicity (specific lysis > 15%). In blocking experiments, the AuTu proliferative reactivity of three TCC from one patient was strongly inhibited by anti-DR and anti-DQ mAbs, whereas that of three TCC from another patient was not affected by either anti-MHC class I or class II (DR, DP, DQ) mAbs. These findings suggest that the recognition of autologous B-NHL cells by AuTu proliferative TCC may occur through MHC-restricted as well as MHC-unrestricted mechanisms.

Genotype study of non-Hodgkin's lymphoma

DNA from 47 patients with non-Hodgkin's lymphoma (NHL) was studied for immunoglobulin and T-cell receptor (TCR) gene rearrangements with Southern blot hybridization. In 83% of the cases the genotypic changes were consistent with immunophenotypic and morphologic examination. Two cases showed mixed genotype and 9 cases of B-cell NHL (67% of centroblastic, 36% of follicular and 33% of large cell anaplastic) showed a population of cells with TCR gamma rearrangements in addition to immunoglobulin rearranged bands. We compared the TCR gamma variable region usage in these rearrangements in B-cell NHL with T-cell NHL and reactive hyperplasia. In T-cell NHL TCR gamma variable regions located at the 3' part of the variable locus were used more often, whilst in B-cell NHL regions of the 5' portion of the locus were preferentially used. Our results confirm the genotypic heterogeneity of histologically defined subtypes of NHL.

Novel tumor-associated accessory molecules involved in the gamma/delta cytotoxic T-lymphocyte-Burkitt's lymphoma interaction

BACKGROUND

Tumor specific cytotoxic T lymphocytes (CTL) recognize antigen via the T-cell receptor (TCR). In addition, recognition requires accessory molecules involved in adhesion and signal transduction. The authors previously have characterized an autologous, Burkitt's lymphoma specific CTL line that uses the gamma-delta TCR to recognize antigen in a nonclassical context. The current study was undertaken to identify novel accessory molecules involved in this unusual TCR-tumor cell interaction.

METHODS

A panel of monoclonal antibodies was generated against a Burkitt's lymphoma cell line and was screened for inhibition of autologous, tumor specific, cytolysis by a gamma-delta CTL line. Proteins identified by these monoclonal antibodies were further characterized by fluorescent-activated cell sorter analysis, Western blot and immunoprecipitation.

RESULTS

Three known (CD5, CD43, and CD11a/CD18) and three novel (BAM-1, BAM-2, and BAM-3) cell surface molecules involved in the gamma-delta CTL-Burkitt's lymphoma interaction were identified and characterized.

CONCLUSIONS

This study identifies and provides a preliminary characterization of three novel Burkitt's lymphoma-associated molecules involved in the gamma-delta CTL-tumor cell interaction and demonstrates that CD5, CD43, and CD11a/CD18 are involved in this interaction. It is likely that other unidentified accessory molecules are also involved in this and other effector cell-tumor interactions. Identification of such molecules may be useful in the design of new immunotherapeutic approaches.

A self-reactive class I-restricted T-cell response of H-2b mice to determinants of the V beta 8.2 domain of the T-cell receptor for antigen

We studied the induction of a self-reactive cytotoxic T lymphocyte (CTL) response to determinants of the variable V beta 8.2 region of the beta-chain of the T-cell receptor (TCR) for antigen in C57BL/6 (H-2b) mice. A CTL response was elicited in vivo by TCR peptide vaccination, and detected in vitro using syngeneic transfectants expressing a rearranged V beta 8.2+ TCR beta-chain. The first series of experiments used a 15-mer peptide representing residues 68-82 of the V beta 8.2 domain and containing Kb and Db allele-specific motifs. Immunization with this peptide stimulated an autoreactive CTL response that cross-reacted with V beta 8.2 epitopes presented by transfectants endogenously processing a V beta 8.2+ TCR beta-chain. These transfectants expressed a construct derived from a murine, rearranged V beta 8.2/D beta 2/J beta 2.3/C beta 2 TCR beta-chain cDNA. The V beta 8.2+ T-cell subset of peptide-primed mice was not deleted but its proliferative response to stimulation by the V beta 8.2-specific monoclonal antibody (mAb) F23.2 was suppressed. In a second series of experiments we immunized mice with a 23-mer peptide representing residues 41-63 of the V beta 8.2 domain that does not contain putative, allele-specific H-2b class I-restricted motifs. This TCR peptide vaccination stimulated a CD8+ CTL response reacting against syngeneic, peptide-pulsed targets but not cross-reacting against transfectants processing/presenting epitopes of the beta-chain. V beta 8.2+ T cells of these peptide-primed mice were not anergized. These data demonstrate that vaccination with an immunogenic peptide representing a naturally processed epitope of the V beta 8.2 domain of the TCR beta-chain induces a self-reactive CD8+ CTL specific for this V beta 8.2 epitope; and anergizes (but does not delete) V beta 8.2+ T cells.

Analysis of T-cell receptor expressing lymphocytes infiltrating squamous cell carcinomas of the upper aerodigestive tract

T-lymphocytes expressing T-cell receptors (TCRs) of the gamma/delta type have been suggested to play an important role in mucosal defense against infection and neoplastic transformation. In this study, an immunohistochemical investigation was performed on the distribution of alpha/beta and gamma/delta TCRs among tumor-infiltrating lymphocytes. Thirteen patients with squamous cell carcinomas of the upper aerodigestive tract were studied, using monoclonal antibodies and an avidin-biotin-peroxidase technique. Most of the T-cells had an alpha/beta TCR. Only 1.6% of the T-cells within the cancer tissue and 1.2% of the T-cells in the parenchyma adjacent to the cancer tissue expressed gamma/delta TCRs. These results are consistent with the results of similar studies in bronchial and breast carcinomas. Biopsies from normal oral mucosa in nine healthy individuals showed that 1.3% of the T-cells within the epithelium and 1.0% of those in the lamina propria adjacent to the epithelium expressed gamma/delta TCRs. Quantitatively the results do not support the theory that gamma/delta T-cells play an important role in the immunological response against cancer tissue in the mucosa of the upper aerodigestive tract. The functional role of these cells in the mucosa and in response to carcinomas is, however, still uncertain.

Activation of cellular immunity after intracavitary monoclonal antibody therapy of ovarian cancer

BACKGROUND

Murine monoclonal antibodies (MoAbs) are now used for targeted tumor therapy. A major obstacle in their successful application is the development of a humoral antiglobulin response, which limits the use of repeated cycles of therapy. The cellular aspects of that response are not well understood.

METHODS

Fifteen patients who had one (12 patients) or two (3 patients) courses of MoAb treatment, 13 age-matched patients with the same histologic types of tumors who had not received MoAbs, and 4 healthy control subjects were studied. Peripheral blood mononuclear cells (PBMCs) were obtained and tested for the ability of T-cells to proliferate in vitro in the presence of the MoAb administered for therapy (HMFG1), a control antibody (11.4.1), and, in some cases, their F(ab')2 fragments. In addition, PBMCs from these patients were phenotyped after in vitro MoAb stimulation with antibodies against CD2, CD3, CD4, CD8, CD16, CD20, CD25 (interleukin-2 receptor [IL-2R]), CD45RA, and UCHL1, and the production of interleukin-2 (IL-2) was evaluated by the CTLL-2 bioassay.

RESULTS

A dose-dependent in vitro T-cell proliferation was observed in 13 of the 15 patients after MoAb therapy. This was not observed in the pretherapy group of patients or healthy control subjects. The mean stimulation index (SI) in the posttherapy group was significantly higher than that of the pretherapy patients and that of healthy control subjects (P = 0.007). When the in vitro T-cell proliferative responses of these patients were measured in the presence of HMFG1 MoAb (IgG1) and 11.4.1 MoAb, there was no significant difference in the mean SI for HMFG1 versus 11.4.1 for the whole group of treated patients (P = 0.67). A significant increase in the mean SI was observed in the presence of HMFG1 over 11.4.1 and their F(ab')2 fragments (P = 0.02) in patients treated twice. A significant increase in the percentage of cells expressing IL-2R was observed after in vitro MoAb stimulation. CD4+ lymphocytes, particularly the CD4+/UCHL1+ memory, the CD4+/IL-2R+ subpopulation, and the CD4/CD8 ratio, increased in all the cases studied after MoAb stimulation, where B-cell and natural killer-cell numbers remained relatively constant (< 2-3%). A sixfold increase was found in the production of IL-2 in PBMC supernatants after MoAb stimulation.

CONCLUSIONS

Mouse MoAbs administered to patients with cancer can lead to the generation of T-cells, which can recognize these MoAbs as antigens and therefore refocus the host's cellular immune response against the targeted tumor. The main proliferating population appears to be CD4+ T-lymphocytes, which after stimulation can release IL-2. Multiple treatments may lead to the generation of T-cells with specificity for the idiotypic component of the administered MoAb.

Synthetic peptide ligands of the antigen binding receptor induce programmed cell death in a human B-cell lymphoma

Peptide ligands for the antigen binding site of the surface immunoglobulin receptor of a human B-cell lymphoma cell line were identified with the use of filamentous phage libraries displaying random 8- and 12-amino acid peptides. Corresponding synthetic peptides bound specifically to the antigen binding site of this immunoglobulin receptor and blocked the binding of an anti-idiotype antibody. The ligands, when conjugated to form dimers or tetramers, induced cell death by apoptosis in vitro with an IC50 between 40 and 200 nM. This effect was associated with specific stimulation of intracellular protein tyrosine phosphorylation.

Antigens recognized by gamma delta T cells

Recent evidence demonstrates the important role played by gamma delta T cells in resistance to infections. Despite this, in most cases the antigens recognized by the responding gamma delta T cells are unknown. Antigen recognition by some gamma delta T-cell populations may not require the participation of either MHC class I or class II molecules. In other cases, evidence exists for the participation of MHC-encoded molecules, particularly non-classical class I molecules.

An analysis of the relationship between gamma delta T cell receptor V gene usage and non-major histocompatibility complex-restricted cytotoxicity

gamma delta T cells are capable of mediating non-major histocompatibility complex (MHC) restricted lysis of a variety of tumour cell lines. The mechanism of this lysis and its significance in tumour immunity are not clear. We have used a panel of five malignant mesothelioma (MM) cell lines, as well as standard tumour targets K562 and Daudi, to investigate some of the factors which could be involved in non-MHC restricted cytotoxicity mediated by gamma delta T cells. Individual MM cell lines, representing a panel of lines derived from a single cell type, varied in their susceptibility to lysis by gamma delta T cell clones. Individual gamma delta T cell clones also showed unique cytotoxic profiles, and differed in their cytotoxic potential. T cell receptor (TCR) V gamma gene usage correlated with the ability of clones to lyse Daudi or K562; clones lysing Daudi expressing V gamma 9 and clones lysing K562 expressing V gamma I subgroup genes. No strict correlation between V gamma and V delta gene usage and MM reactivity was, however, demonstrable. There was also no correlation between gamma delta T cell lysis of MM cell lines and the capacity of gamma delta T cells to produce interferon-gamma, tumour necrosis factor-alpha, interleukin-2 or interleukin-4, nor with their expression of CD8.

Processing and presentation of idiotypes to MHC-restricted T cells

Among the self antigens, immunoglobulins, and in particular idiotypes, are of special interest because of their extreme sequence heterogeneity and their postulated involvement in regulatory interactions in the immune system. We have therefore studied antigen processing and presentation of variable region peptides, processed idiotypes, to MHC class II molecule-restricted T cells. The immunoglobulin used has been the lambda 2(315) light chain produced by the BALB/c MOPC 315 plasmacytoma (alpha, lambda 2). The minimum length of a stimulatory synthetic idiotypic peptide comprises residues 91-101 of lambda 2(315) and is presented by the I-E(d) molecule to CD4+ T cells. T cell clones with specificity for the 91-101(lambda 2(315))/I-E(d) complex utilize a limited TCR repertoire and are of both Th1 and Th2 type. For presentation, extracellular lambda 2(315) requires endocytosis and processing, as previously described for conventional exogenous antigens. In addition, a B lymphoma cell can process and present its own endogenous lambda 2(315). This was shown by transfecting manipulated lambda 2(315) gene variants into B lymphoma cells, followed by evaluation of the APC function of the transfectants. These studies demonstrated that surface expression or secretion of lambda 2(315) is not necessary for presentation and suggested that the endoplasmic reticulum may be a processing compartment. To extend our findings to naive Id+ B cells and anti-Id T cells, we have generated lambda 2(315)-transgenic as well as TCR-transgenic mice. A model is presented for a T-B cell interaction based on presentation of processed idiotypes.