Human CD3+4-8-WT31- T lymphocyte populations expressing the putative T cell receptor gamma-gene product. A limiting dilution and clonal analysis

Gammadelta receptor bearing T cells in scleroderma: enhanced interaction with vascular endothelial cells in vitro

In view of the documented perivascular mononuclear cell infiltration in the involved organs in scleroderma (SSc) and the reported accumulation of gammadelta-T cells in SSc skin and lung, we evaluated gammadelta-T cell interaction with endothelial cells (EC) in vitro. gammadelta- and alphabeta-T cells were isolated from BPMN of SSc patients with early diffuse disease and of matched control subjects by an immunomagnetic method after stimulation with mycobacterium lysate and interleukin-2 for 2 weeks. Lymphocyte adhesion, proliferation, and cytotoxicity to EC were investigated. SSc gammadelta-T cells adhered to cultured EC and proliferated at higher rates than control cells. Furthermore, significant EC cytotoxicity by SSc gammadelta was seen. The cytotoxicity was blocked by addition of anti-gammadelta-TCR antibody and by anti-granzyme A antibody but not by anti-MHC class I and II antibodies. Expression of granzyme A mRNA was seen in five/five SSc gammadelta-T cells and in one/five control cells. alphabeta-T cells from both SSc and control subjects were significantly less interactive with EC than gammadelta-T cells. The data demonstrate EC recognition by SSc gammadelta-T cells and propose gammadelta-T cells as a possible effector cell type in the immune pathogenesis of SSc.

Immunoreactivity of the central nervous system in cats with a Borna disease-like meningoencephalomyelitis (staggering disease)

The inflammatory cell composition and the expression of major histocompatibility complex (MHC) antigens in the central nervous system (CNS) of 13 cats with a spontaneous, Borna disease-like meningoencephalomyelitis (staggering disease) was investigated by immunohistochemistry with a panel of monoclonal and polyclonal antibodies. T lymphocytes were the predominating inflammatory cells within the adventitial space. CD4+ T cells were more abundant than CD8+ T cells. Scattered IgG-, IgA- and IgM-containing cells were found in the adventitial space and surrounding neuropil, often adjacent to neurons. There was a markedly increased MHC class II expression in cells morphologically resembling microglia. In several cats, Borna disease virus specific antigen was detected, but only in a few cells, mainly of macrophage character. Our findings indicate a long-standing inflammatory reaction in the CNS of cats with staggering disease, possibly triggered and sustained by a persistent viral infection.

Functional analysis of TCR gamma delta+ T cells in tumour-infiltrating lymphocytes (TIL) of human pancreatic cancer

In six patients with advanced pancreatic carcinoma, TIL and tumour-draining lymphocytes (TDL) were isolated from primary pancreatic tumour and regional lymph nodes. In comparison with TDL and peripheral blood lymphocytes (PBL), TIL contained a comparatively higher percentage of TCR gamma delta+ cells, although they were still a small fraction. By 2 weeks culture with rIL-2 and immobilized OKT-3 antibody, the TCR gamma delta+ cells in TIL were preferentially expanded at the early culture periods, although it was temporary. In four cases, the TCR gamma delta+ and CD8+ TCR alpha beta+ TIL were separated by negative sorting using flowcytometry. All the TCR gamma delta+ TIL were CD4-, CD8- (double negative), and one of the TIL lines was mostly composed of delta TCS1+ cells, while the others were delta TCS1-. In comparison with CD8+ TCR alpha beta+ TIL, all the TCR gamma delta+ TIL exhibited much stronger lytic activity against freshly isolated autologous pancreatic cancer cells. However, all the gamma delta+ TIL also exhibited a strong non-MHC-restricted cytotoxicity, and there was no correlation between the lytic pattern and the percentage of delta TCS1+ cells. These data suggest that the TCR gamma delta+ T cells can proliferate vigorously in a certain condition, and if successfully expanded in vitro they might be helpful material for effective adoptive immunotherapy.

Analysis of T cell receptors in rheumatoid arthritis: the increased expression of HLA-DR antigen on circulating gamma delta+ T cells is correlated with disease activity

The phenotypic characteristics of peripheral blood T cells, isolated from 37 rheumatoid arthritis (RA) patients and 17 healthy controls were determined with special emphasis on gamma delta+ T cells and CD4-CD8- alpha beta+ T cells. Two- and three-colour automated flow cytometry analyses were performed using a panel of MoAbs directed against differentiation antigens and T cell receptor molecules. The results demonstrated: (i) no significant difference between the percentages of CD4-CD8- alpha beta+ T cells in patients and controls; (ii) a significant decrease of the gamma delta+ T cell level in the peripheral blood of RA patients relative to controls; (iii) phenotypic abnormalities of circulating gamma delta+ T cells in RA patients suggestive of an activation status in vivo. These abnormalities included a significant reduction in the density of the T cell differentiation antigen CD3 and an increase in the expression of HLA-DR antigen. The level of circulating HLA-DR+/gamma delta+ T cells was significantly higher in patients with active disease. HLA-DR+/gamma delta+ T cells were also present in the synovial fluid obtained from three patients with an active disease. In addition, preliminary experiments showed that the activated gamma delta+ T cells were predominantly V delta 1. Taken together, these data support the involvement of gamma delta+ T cells in the pathogenesis of RA.

Functional and morphologic characterization of human T lymphocytes expressing the TCR gamma/delta

A minor subset of T lymphocytes express a TCR composed of gamma and delta chains. This subset differs from conventional T cells for a number of phenotypic and functional characteristics. TCR gamma/delta+ cells simultaneously lack both CD4 and CD8 antigens. Cloning of CD4-8- peripheral blood lymphocytes, under limiting dilution conditions, revealed that they are homogeneously composed of cytolytic cells which efficiently lyse tumor target cells. Formal proofs have been provided that TCR gamma/delta+ cells are able to recognize antigens. For example, they proliferated in response to allogeneic mixed lymphocyte culture (MLC); in addition, MLC-derived TCR gamma/delta+ cells specifically lysed PHA-induced blast cells bearing the stimulating alloantigens. The selection of monoclonal antibodies specific for TCR gamma/delta molecules allowed to identify two distinct subsets of TCR gamma/delta+ cells. Both of these mABs, termed BB3 and delta TCS-1 respectively, induced specific activation of cloned cells expressing the corresponding antigenic determinants (as assessed by measurements of intracellular Ca++ and/or lymphokine production or cytolytic activity). Analysis of the distribution of subsets expressing different forms of TCR gamma/delta, showed that the BB3-reactive form is prevalent in the peripheral blood. In contrast, delta-TCS-1-reactive cells are relatively infrequent in peripheral blood but represent the majority of TCR gamma/delta+ cells in tissues.

Targeting of «T» Lymphocytes against Human Hepatoma Cells by a Bispecific Monoclonal Antibody: Role of Different Lymphocyte Subsets

In an attempt to construct bispecific monoclonal antibodies (bimAbs) able to target cytotoxic T lymphocytes against human hepatoma cells, an HGPRT-deficient mutant of the Hepama-6 hybridoma, which produces an antihuman-hepatoma mAb, was directly fused with splenocytes from Balb/C mice immunized by a polyclonal cytotoxic T-cell line. Hybrid hybridomas were selected in HAT medium, and their supernatants were directly screened for the ability to induce IL-2-cultured cytotoxic T lymphocytes to kill hepatoma cells in a 51Cr-release assay. The selected hybrid hybridoma, termed DQ-33, secretes a bimAb, which reacts with a CD3-associated determinant. When resting peripheral-blood lymphocytes were used as effector cells, virtually no cytolytic activity could be induced by DQ-33, whereas phytohemagglutinin-activated lymphocytes that had been expanded in vitro in IL-2-containing medium could be efficiently targeted against hepatoma cells. Targeting by DQ-33 bimAb was analyzed on different subsets of IL-2-cultured lymphocytes. It was evident that CD+4–8+ TCRα/β+ and CD3+4–8-TCRγ/δ+ lymphocytes were efficiently induced by bimAb to lyse human hepatoma cells, whereas no induction of cytolysis could be observed when CD3 + 4+8-TCRα/β+ cells were used as effectors. DQ-33 bimAb was also able to induce lymphokine secretion (IL-2, GM-CSF and TNF-α) by all the different subsets of lymphocytes analyzed in the presence of target cells expressing the relevant antigen, independent of the expression of cytolytic activity.

Molecular and cellular analysis of human T lymphocytes expressing gamma delta T-cell receptor

A minor subset of T lymphocytes expresses a CD3-associated TCR composed of gamma and delta chains. The majority of TCR gamma/delta+ cells lack surface CD4 and CD8 antigen and do not react with WT31 mAb. These negative criteria were utilized in early studies to identify TCR gamma/delta+ cells. More recently, mAb to TCR gamma/delta, selected in different laboratories, have permitted the direct identification of TCR gamma/delta+ cells and their subsets. TCR gamma/delta molecules were found to be heterogeneous in size and charge mobility. Two major forms of TCR gamma/delta could be identified that are characterized by the presence or absence of an inter-chain disulphide bond. Biochemical analysis originally suggested that a precise correlation existed between reactivity with BB3 or delta TCS1/A13 mAb and expression of a disulphide (C gamma 1-encoded) or non-disulphide linked (C gamma 2-encoded) form of TCR gamma/delta. However, more recent studies have indicated that these mAb react with the molecular product of V delta 2 or V delta 1, respectively, mAb directed to one or another form of TCR gamma/delta activate the functional program of the cell, leading to intracellular Ca++ mobilization, lymphokine production and triggering of the lytic machinery. Analysis of the target molecules for TCR gamma/delta-mediated recognition revealed that at least some TCR gamma/delta+ cells are capable of specific responses to (allo)antigen and that polymorphic determinants of class I molecules can be recognized (as shown by the specific lysis of P815 cells transfected with HLA-24 allele). Unlike TCR alpha/beta+ cells, TCR gamma/delta+ cells are homogeneously composed of cytolytic precursors, as shown by the analysis of a large panel of clones in both lectin-dependent and redirected killing assays. In spite of their LGL morphology, freshly isolated TCR gamma/delta+ cells do not lyse NK-sensitive targets but do so after exposure to rIL-2. A modest cytolytic activity, however, could be induced also in fresh cells by anti-TCR/CD3 mAb in a redirected killing assay. Analysis of the distribution of the subsets expressing different TCR gamma/delta types showed that BB3+ cells are prevalent in the peripheral blood and virtually absent in the thymus; in contrast, A13+ (delta TCS1+) cells represent the majority of TCR gamma/delta+ thymocytes. Electron microscopic analysis of fresh TCR gamma/delta+ cells showed an extended cytoplasm containing numerous electron-dense granules identifiable as primary lysosomes. Upon stimulation with IL-2, TCR gamma/delta+ cells, similar to other LAK cells, display an increase in their cytoplasmic granules together with a redistribution of cytoskeletal structures.(ABSTRACT TRUNCATED AT 400 WORDS)

T gamma delta cells and their subsets in blood and synovial tissue from rheumatoid arthritis patients

We have examined the frequencies of T gamma delta cells in blood, synovial fluids, and synovial membranes of patients with rheumatoid arthritis (RA) and in blood from age-matched controls. Immunocytochemical and immunohistochemical techniques were used with monoclonal antibodies BB3 and A13 to define a major and minor blood subset of T gamma delta cells respectively. Together, these antibodies identify the majority (if not all) of the peripheral blood T gamma delta cells. Significantly lower levels of T gamma delta cells were found in the blood of RA patients compared with controls, whilst higher but not significant numbers were found in the synovial fluids of paired samples. Scattered T gamma delta cells were found only in some synovial membranes with a distribution similar to the T alpha beta cells. Analysis of the two different T gamma delta-cell subsets indicated a ratio of BB3 to A13 of about 5:1 in control and RA blood. However, this ratio was less than 1:1 in the RA synovial fluids and membranes. The migratory nature of the A13+ cells could account for their predominance in these sites. The possible pathological significance of these cells in the rheumatoid synovial fluid and synovial membranes is discussed.

T gamma delta-cell subsets in cord and adult blood

A minor population of T cells expresses a heterodimeric antigen receptor composed of gamma and delta chains (TcR-1). In blood from adults, two subsets of T gamma delta cells can be identified by the monoclonal antibodies (MoAb) BB3 and A13. Little is known about the distribution and markers of these subsets early in life. We have therefore examined both the frequencies of these cells in cord blood and their expression of the cytotoxicity-associated marker serine esterase (SE), using immunocytochemical techniques. Our data show lower percentages of TcR-1+ cells in the blood of newborns compared with that in adults. However, the ratio of the A13+/BB3+ cells was significantly higher in cord than in adult blood. Whereas virtually all the adult TcR-1+ cells in blood were SE-positive, only a small proportion of the cord blood cells carried this enzyme. This was restricted to the BB3+ T gamma delta-cell subset in the cord. Our data suggest different characteristics of the TcR-1+ cells in blood from newborns compared with adult blood, and study of the functions of the different subsets, e.g. cytotoxicity, will be important in understanding their particular role in immunity.

Characterization of normal human CD3+ CD5- and gamma delta T cell receptor positive T lymphocytes

The functional and phenotypic properties of normal human CD3+CD5- T cells which have a higher frequency of cytotoxic cells than CD3+CD5+ T lymphocytes have been described. Using three- and four-colour immunofluorescence flow cytometric cell sorting, the CD3+CD5- and CD3+CD5+ populations were subdivided into alpha beta or gamma delta T cell receptor positive cells. The four subsets were examined for the in vitro cytotoxic activity and were also stimulated with mitogens in limiting-dilution assays to measure the frequencies of proliferating and interleukin-2 (IL-2) producing cells. CD3+CD5- alpha beta +, CD3+CD5- gamma delta + and CD3+CD5+ gamma delta + cells had lower frequencies of proliferating and IL-2-producing cells than did CD3+CD5+ alpha beta + cells. However, the cytotoxic activity of the different phenotypes was higher in the CD3+CD5- subsets, especially when these cells were gamma delta +. Expression of gamma delta or lack of expression of CD5 appeared to be associated with the acquisition of cytolytic potentials. CD8 was expressed on 20% of fresh CD3+ gamma delta + cells. Cultured gamma delta + cells retained the expression of gamma delta, but quickly lost that of CD8 and with time modulated the expression of CD5. The expression of CD5 was found to be higher on sorted CD3+CD5+ gamma delta - than on CD3+CD5+ gamma delta + cells. These observations indicate that gamma delta is preferentially expressed on CD5-negative or weakly positive T lymphocytes and that CD3+CD5- gamma delta + cells appear to constitute a discrete small subset of mature T lymphocytes which are cytotoxic in nature. However, the exact immunological function of these cells and their place in T cell ontogeny are yet to be elucidated.

Molecular analysis of human gamma/delta+ clones from thymus and peripheral blood

We analyzed the V gamma and V delta gene usage in TCR-gamma/delta-bearing T cell clones isolated from human peripheral blood and postnatal thymus using V-specific mAbs and Southern and Northern analyses. In peripheral blood most of the gamma/delta cells express the V gamma 9-JP-C gamma 1 chain paired with a delta chain bearing the V delta 2 gene product. This heterodimer is very rare in the postnatal thymus, where a different and less restricted pairing of V gamma 9 and V delta 2 chains is found. These findings indicate that physical constraints cannot explain the overrepresentation of a particular V gamma 9-JP/V delta 2 heterodimer in the peripheral blood, and we discuss alternative mechanisms that may account for this differential distribution. In addition, this analysis allowed us to map the specificity of the delta TCS1 mAb to V delta 1-J delta 1 and to identify at least five different expressed V delta genes.

Surface molecules involved in the activation and regulation of T or natural killer lymphocytes in humans

The surface molecules that mediate activation of different subsets of T or NK cells have been reviewed. A suitable approach to the study of different lymphocyte activation pathways is provided by mAbs specific for these molecules. MAbs directed to the CD3 surface molecules mediate a polyclonal T-cell activation, whereas mAbs to "clonotypic" structures of TCR only trigger cells bearing the corresponding clonotypic determinant (thus mimicking the effect of antigen/MHC). MAbs directed to appropriate epitopes of CD2 molecules or to CD28 molecules mediate polyclonal T-cell activation, leading to triggering of the functional program of the cell (i.e. proliferation, lymphokine production or activation of the cytolytic machinery). Interaction of specific mAbs with CD3/TCR molecules leads to surface modulation of these molecules which lasts for 48-72 h. During this interval the cell is refractory to any further activation stimulus. No such refractoriness occurs following mAb-induced modulation of CD2 or CD28 surface molecules. The mechanisms by which CD3/TCR modulation results in the inactivation of T-cell function appears to involve the early metabolic steps of T-cell activation, as neither Ca++ mobilization nor IP3 formation could be further induced by any stimulus. The surface molecules and mechanisms involved in the activation of TCR gamma/delta cells are similar to those of TCR alpha/beta + cells. TCR gamma/delta molecules are heterogeneous in size and charge mobility. MAbs directed to one or another form of TCR gamma/delta trigger the functional program of the cell (primarily cytolytic function). However, a receptor form composed of a heavy form (55 kD) of the gamma chain appears to be relatively inefficient in signal transduction upon binding with anti-TCR mAbs. Evidence has also been provided that TCR gamma/delta + cells are capable of (allo)antigen responses and that polymorphic determinants of class I can be recognized (specific lysis of P815 cells transfected with HLA-A24 allele). Although the mechanisms and the surface receptor molecules involved in (CD3-, CD16+) NK cell activation are still poorly understood, several surface molecules have been identified that mediate NK-cell triggering. These include CD2 and CD16 and the novel GL183 molecule which is selectively expressed by a fraction of NK cells and thus identifies a well-defined NK subsets. Under appropriate conditions, mAbs to CD16 or GL183 mediate an inhibitory effect on the NK cell activation. These data suggest that also NK cells are characterized by surface molecules capable of initiating distinct pathways of cell activation and that, similarly to T lymphocytes, mechanisms exist which regulate NK cell function.

Re-targeting of human lymphocytes expressing the T-cell receptor gamma/delta to ovarian carcinoma cells by the use of bispecific monoclonal antibodies

TcR gamma/delta+ lymphocytes represent a small subset homogeneously composed of cytolytic T cells displaying unique motility and homing properties. Since the lytic machinery of these cells can be efficiently triggered by monoclonal antibodies (MAbs) directed to the TcR gamma/delta, such MAbs were used for the construction of bispecific MAbs in conjunction with an MAb specific for ovarian carcinoma cells. Hybrid hybridomas were obtained by fusing the Mov19 MAb (IgG2a)-producing hybridoma with either GI (IgG2a) or A13 (IgG1) hybridomas, secreting MAbs specific for 2 peripheral blood subsets of TcR gamma/delta+ lymphocytes. Hybrid hybridomas producing bispecific MAbs were screened according to their ability to induce ovarian carcinoma (IGROVI) target cell lysis by GI+ or A13+ T cell clones, respectively. The GI-derived GM33.9 bispecific MAb induced selective lysis of Mov19+ ovarian carcinoma target cells only by GI+ clones, whereas the A13-derived AM18.4 MAb was effective only in combination with A13+ clones. Neither the anti-TcR gamma/delta nor the Mov19 parental MAbs (used alone or in combination) induced target-cell lysis. The hybrid nature (IgG1/IgG2a) of the AM18.4 bispecific MAb was indicated by 2-color immunofluorescence experiments. Thus, both ovarian carcinoma and A13+ effector cells were double stained by AM18.4 bispecific MAb followed by PE-conjugated anti-IgG1 and FITC-conjugated anti-IgG2a second reagents. Polyclonal TcR gamma/delta+ cells were obtained by direct stimulation of peripheral blood mononuclear cells with Sepharose bead-conjugated anti-TcR gamma/delta MAbs and IL-2. The lines so obtained contained more than 90% of TcR gamma/delta+ cells after 4 weeks of culture, with an increase in TcR gamma/delta+ cell numbers ranging from 200 to 1,000-fold. These TcR gamma/delta+ cell lines efficiently lysed ovarian carcinoma target cells in the presence of bispecific MAb and may therefore represent a suitable source of effector cells for induction of ovarian carcinoma cell lysis.

Subpopulations of human peripheral T gamma delta lymphocytes

In the search for the genes encoding the alpha and beta chains of the T-cell receptor, Tonegawa et al. discovered a third class of rearranging T-cell specific genes. This finding led them to postulate the existence of additional forms of T-cell receptors. In this article, Frédéric Tribel and Thierry Hercend briefly discuss recent results, which may help in the delineation of human peripheral blood gamma delta+ subsets based on the molecular structure of this receptor.

Human CD4-8- -derived clones. Phenotypic and functional characteristics and variation between donors in patterns of T-cell receptor gamma gene rearrangements

Clones were derived from highly purified human CD4-8- lymphocytes from three different donors and maintained in the presence of interleukin 2 and phytohaemagglutinin. Considerable variation was noted between donors in the phenotype and T-cell receptor (TCR) gamma gene rearrangements of CD4-8- -derived clones. In one donor, most clones remained CD4-8- and all were CD3+WT31- and therefore expressed gamma/delta heterodimers. TCR gamma gene rearrangements almost all involved C gamma 1. In contrast, most clones from a second donor were CD3+WT31+, and therefore expressed alpha/beta heterodimers, and many were positive for CD4 or CD8. Most clones from a third donor were CD3+WT31- with a high proportion of TCR gamma gene rearrangements involving C gamma 2. The V gamma 9JP rearrangement was exclusively confined to CD3+WT31- clones and was present in the majority of clones. Almost all CD3+WT31- clones showed TCR beta as well as gamma gene rearrangements. Most CD3+WT31- clones with at least one chromosome rearranged to C gamma 1 exhibited high non-major histocompatibility complex (MHC)-restricted cytotoxic activity, while most of those with two C gamma 2 rearrangements, and therefore expressing a non-disulphide-linked gamma/delta heterodimer, had low activity. Preincubation of effector cells with anti-CD3 strongly inhibited the cytotoxicity of CD3+WT31- clones while that of CD3+WT31+ clones was enhanced. This implicates the CD3-gamma/delta complex in target cell recognition by cytotoxic gamma/delta-bearing T-cell clones. The results show that there is heterogeneity between donors in the relative proportions of CD4-8- -derived clones expressing alpha/beta heterodimers and the different forms of the gamma/delta heterodimer.

Most human CD3+WT31- clones with T cell receptor C gamma 1 rearrangements show strong non-MHC-restricted cytotoxic activity in contrast to those with C gamma 2 rearrangements

Clones expressing CD3 in the absence of WT31 expression were obtained by growing highly purified WT31- cells in the presence of interleukin 2 and phytohemagglutinin. Most clones showed rearrangements of T cell receptor (TcR) gamma genes on both chromosomes involving all five currently identified J gamma segments. About a third of these clones had a rearranged 12 kb Kpn I band with the J gamma probe, consistent with a V9JPC gamma 1 rearrangement. All clones with both chromosomes rearranged to C gamma 2 had low or intermediate cytotoxic activity while most of those with at least one chromosome rearranged to C gamma 1 had high cytotoxic activity against both natural killer-sensitive and natural killer-resistant targets. This applied both to clones with and without the V9JPC gamma 1 rearrangement. Of three clones with both C gamma 1 and C gamma 2 rearrangements two had high activity and the other was only weakly cytotoxic. In addition, most clones showed rearrangement of TcR beta genes. Some clones were capable of secreting levels of interferon-gamma and tumor necrosis factor-alpha which were as high as those produced by CD3+4+WT31+ T cell clones. The results suggest that most human CD3+WT31- clones expressing a disulfide-linked C gamma 1/delta heterodimer are capable of mediating strong non-major histocompatibility complex-restricted cytotoxicity whereas those expressing non-disulfide-linked C gamma 2/delta heterodimers are not.

Surface molecules involved in CD3-negative NK cell function. A novel molecule which regulates the activation of a subset of human NK cells

Natural killer cells are characterized by the lack of CD3/TCR molecules and by the expression of CD16 and CD56 (NKHI or Leu19) surface antigens. In addition to their ability to lyse certain tumor target cells, they release lymphokines including tumor necrosis factor and interferon gamma. Another unexpected functional capability of at least some NK cells is the ability to specifically recognize and lyse certain normal allogeneic cells (PHA-induced blasts). MAbs directed to CD2 or to CD16 surface molecules induced triggering of NK cells leading to target cell (p815) lysis in a redirected killing assay. Importantly, different from induction of T cell activation, single anti-CD2 MAbs were sufficient to trigger NK cell function. Another MAb (GL183) inducing NK cell triggering recognized a novel surface molecules expressed on 20-50% of resting or cultured NK cells. Cloned GL183+ cells displayed a variable degree of cytolytic activity against a number of human target cells of different histotype; moreover, this activity was strongly enhanced by the addition of GL183 MAb. On the other hand, GL183 MAb inhibited lysis of murine lines (including P815). Thus on P815 target cells GL183 MAb has an effect antithetical to that of other stimuli including PHA, anti-CD2 or anti-CD16 MAbs. GL183 MAb, added simultaneously to one or another of the stimuli above, strongly inhibited the target cell lysis induced by these stimuli. Thus, GL183 may represent an important molecule in the process of activation/regulation of phenotypically-defined NK cell subsets.

Human T lymphocytes expressing gamma/delta T cell antigen receptor

The majority of mature T lymphocytes express CD3-associated antigen receptor molecules (TCR) formed by alpha and beta chains. Recently, a minor subset has been identified that expresses a different CD3-associated heterodimer composed of gamma and delta chains. The TCR gamma/delta+ cell subset differs from conventional T cells for a number of phenotypic and functional characteristics. The simultaneous lack of both CD4 and CD8 antigens allows to greatly enrich TCR gamma/delta+ cells (by monoclonal antibodies and complement). Cloning of CD4-8- peripheral blood lymphocytes, under limiting dilution conditions, revealed that they are homogeneously composed of cytolytic cells which, in most instances, lyse tumor target cells. The formal proof has been provided that TCR gamma/delta+ cells are able to recognize antigens. Indeed they proliferated in response to allogeneic cells in mixed lymphocyte culture (MLC) and MLC-derived TCR gamma/delta+ cells specifically lysed PHA-induced blast cells bearing the stimulating alloantigens. The use of different monoclonal antibodies specific for TCR gamma/delta molecules allowed to identify two distinct subsets which bound BB3 and delta-TCS-1 mAbs, respectively. The BB3-reactive TCR molecules were represented by C gamma 1-encoded disulfide-linked heterodimers, whereas delta-TCS-1 reacted with C gamma 2-encoded nondisulfide-linked molecules. Both BB3 and delta-TCS-1 mAb induced activation of cloned cells expressing the corresponding antigenic determinants (as assessed by measurements of intracellular Ca2+ and lymphokine production or cytolytic activity). Analysis of the unfrequent delta-TCS-1+ clones which express surface CD8 molecules revealed that the "heavy" 55 kDa form of (C gamma 2-encoded) gamma chain is selectively expressed by this cell type. Analysis of the distribution of subsets expressing different TCR gamma/delta isotypes showed that the C gamma 1-encoded, BB3-reactive form is prevalent in the peripheral blood, but virtually absent in the thymus. In contrast, cells expressing the C gamma 2-encoded, delta-TCS-1 reactive form are relatively unfrequent in peripheral blood, but represent the majority of TCR gamma/delta+ thymocytes. In addition, upon culture in rIL-2, approximately half of the delta-TCS-1+ thymocytes expressed CD8 antigen, thus providing further evidence that major differences exist in the distribution of TCR gamma/delta+ subsets in thymus and in peripheral blood.

Human thymocytes expressing gamma/delta T-cell receptors

Expression of T-cell receptors of gamma/delta type characterizes a small subset of peripheral T lymphocytes which is homogeneously composed of cytolytic cells and, in most instances, lack CD4 and CD8 differentiation antigens. By the use of anti-TCR gamma/delta MAbs it is possible to identify two distinct subsets of TCR gamma/delta+ cells that are characterized by a C gamma 1 or C gamma 2-encoded forms of gamma-chain, respectively. While the BB3 MAb-reactive (C gamma 1 encoded) cell subset is prevalent in peripheral blood (PB), these cells represent less than 10% in TCR gamma/delta+ thymocyte populations. In thymus, the majority of cells was found to react with delta-TCSI (or A13) MAbs. Culture of CD4-8- thymocytes (highly enriched in TCR gamma/delta+ cells) in IL-2 resulted in the de novo expression of CD8 surface antigen and of non MHC-restricted cytolytic activity. Cloning of CD4-8- thymocytes resulted, for the most part, in CD3+ TCR gamma/delta+ cells. Moreover, the majority of clones expressed the unusual delta-TCSI+ CD8+ phenotype and lysed the NK-sensitive K562 target cells. Analysis of the immunoprecipitated TCR molecules showed the existence of the (rare) heavy (55 kDa) form of gamma-chain. A redirected killing assay using murine P815 target cells and appropriate "stimulatory" antibodies was further employed for functional analysis of thymus-derived TCR gamma/delta+ clones. While anti-CD3 MAbs efficiently triggered the cytolytic activity of all clones irrespective of their phenotype, MAbs directed to TCR gamma/delta induced efficient lysis only of BB3+ or delta-TCSI+CD8 clones, but not of delta-TCSI+ CD8+ clones.(ABSTRACT TRUNCATED AT 250 WORDS)

Clonal analysis of CD4-CD8- human thymocytes expressing a T cell receptor gamma/delta chain. Direct evidence for the de novo expression of CD8 surface antigen and of cytolytic activity against tumor targets

CD4-CD8- human thymocytes were obtained by treating total thymocyte suspensions with anti-CD4 and anti-CD8 monoclonal antibodies (mAb) and complement. The resulting cell populations contained virtually no CD4+, CD8+ or WT31+ cells and 17-65% CD3+ cells. In addition, analysis of cell reactivity with delta-TCS-1 mAb (specific for the C gamma 2-encoded, nondisulfide-linked form of TcR gamma/delta), revealed the presence of a variable proportion of delta-TCS-1+ cells (the % of delta-TCS-1+ cells were lower than the percentage of CD3+ cells). Upon culture in recombinant interleukin 2 (IL2, in the presence of irradiated mononuclear cells), CD4-CD8- thymocytes underwent extensive proliferation. In addition, a progressive increase of CD8+ cells (but not of CD4+ or WT31+ cells) could be detected. Cells also progressively acquired cytolytic activity against K-562 or fresh melanoma cells. Fresh CD4-CD8- thymocytes were cloned under limiting dilution conditions. The cloning efficiencies were relatively high (1/3 cells); in addition, virtually all the clonal progenies obtained displayed cytolytic activity and expressed the CD3+WT31-delta-TCS-1+ surface phenotype. About half of the clones analyzed were CD8+, whereas none expressed CD4 antigens. We conclude that (a) only delta-TCS-1-reactive, TcR gamma/delta+ cells can be isolated from CD4-CD8- thymocytes cultured in IL2, and (b) the expression of CD8 antigen and of cytolytic activity reflects a true in vitro phenotypic change of CD8-, noncytolytic precursors (and not the preferential growth of few contaminating cells).

Cloned CD3+ TcR alpha/beta- Ti gamma A- peripheral blood lymphocytes compared to the Ti gamma A+ counterparts: structural differences of the gamma/delta receptor and functional heterogeneity

We have assessed the organization of T cell gamma rearranging genes (TRG) in circulating TcR gamma/delta+ lymphocytes which do not express V gamma 9-encoded Ti gamma A+ gamma chain. Following purification of the minor TcR gamma/delta+ Ti gamma A- fraction, cloned cell lines were developed from peripheral blood of 5 individuals. Out of the 26 clones studied, only 3 TcR gamma/delta+ Ti gamma A- cells were found to express a disulfide-linked C1-encoded gamma chain. The remaining 23 Ti gamma A- clones with a C2-encoded nondisulfide-linked receptor were found to display rearrangements of various V genes to J2 segments on both chromosomes; there was no predominance of a unique rearrangement even though the TRG-V3 and -V4 genes belonging to subgroup I were frequently employed. Together, these findings further strengthen the hypothesis that lymphocytes with a C gamma 1 encoded chain are produced earlier in T cell ontogeny than the C gamma 2 counterparts. The "non-major histocompatibility complex (MHC) requiring" (i.e., "natural killer-like") cytotoxicity mediated by many TcR gamma/delta+ Ti gamma A- cells appeared to be very low as compared to that of Ti gamma A+ clones. Yet, treatment by the OKT3 monoclonal antibody revealed a strong lytic potential in the Ti gamma A- lymphocytes with little, if any, natural killer-like activity. Thus, with respect to the latter function, a substantial heterogeneity is found in cells expressing distinct gamma chains. In an attempt to characterize undefined specificities of Ti gamma A- lymphocytes, they were screened against a panel of Epstein-Barr virus-transformed B cell lines homozygous for HLA-DR1 to DR10 determinants; one of the clones was found to recognize DR7. In light of reports from other groups describing class I-related specificities, it is apparent that TcR gamma/delta+ lymphocytes are able, like the TcR alpha/beta+, to recognize and kill target cells through either an MHC-dependent (with involvement of either class I or class II gene products) or a non-MHC-requiring pathway.

Phenotypic heterogeneity of cerebrospinal fluid-derived HIV-specific and HLA-restricted cytotoxic T-cell clones

A variety of clinical syndromes, including AIDS and neurological disorders, may follow as a consequence of infection with the human immunodeficiency virus type 1 (HIV-1). It is not yet clear, however, to what extent the destruction of lymphocytes and neural cells associated with these conditions is caused by adverse immune responses to HIV-1 or how much is due to cytopathic effects of the virus itself. Here we document the existence of HLA-restricted, HIV-1-specific cytotoxic T lymphocytes in the cerebrospinal fluid of two AIDS patients manifesting neurologic disorders. These cytotoxic T lymphocytes showed dual specificity, recognizing target cells coated with purified HIV-1 envelope glycoprotein (gp 120) or inactivated HIV-1 in the context of HLA antigens. Cytotoxic T-cell clones derived from one of the AIDS patients revealed restriction specificities representing both HLA class I and HLA class II antigens. Considerable phenotypic heterogeneity was observed amongst these clones, some expressing conventional combinations of cytotoxic T-cell surface markers, and others displaying unusual phenotypes. The presence of HIV-specific cytotoxic T lymphocytes in AIDS patients, and in particular in their cerebrospinal fluid, suggests that these cytotoxic effectors may participate in the lymphoid cell and/or neurologic damage observed in such patients.

Synovial microenvironment-T cell interactions. Human T cells bind to fibroblast-like synovial cells in vitro

Synovitis in rheumatoid arthritis is characterized by infiltration of the synovium by T and B lymphocytes and monocytes, as well as by the proliferation of synovial lining cells, fibroblasts, and endothelial cells. To study synovial cell-T cell interactions in vitro, we established cultures of fibroblast-like synovial cells, and used these cells in a synovial cell-T cell binding assay. Using T cells at various stages of differentiation and activation, we found that human thymocytes and mitogen-activated peripheral blood T cells bound to fibroblast-like synovial cells, whereas fresh peripheral blood T cells did not. Moreover, activated T cells from inflammatory synovial tissue or from synovial fluid also bound to fibroblast-like synovial cells cultured in vivo. Antibodies against certain epitopes of the T cell CD2 (35.1) and synovial cell lymphocyte function-associated antigen-3 (LFA-3) (TS2/9) molecules inhibited synovial cell-thymocyte binding. However, these same anti-CD2 and anti-LFA-3 antibodies only partially inhibited synovial cell binding to activated normal peripheral blood T cells. Moreover, T cells from inflammatory synovium from rheumatoid arthritis and psoriatic arthritis patients also bound to synovial cells in vitro. These findings demonstrate that fibroblast-like synovial cells are capable of binding to human T cells in vitro, and suggest that during the course of inflammatory synovitis, synovial fibroblast-T cell interactions may occur in vivo.

Two subsets of human T lymphocytes expressing gamma/delta antigen receptor are identifiable by monoclonal antibodies directed to two distinct molecular forms of the receptor

Two mAbs directed to the TCR-gamma/delta were analyzed for their pattern of reactivity with CD3+WT31- cell populations or clones. In normal individuals, the BB3 mAb reacted with approximately 2/3 of peripheral blood CD3+WT31- lymphocytes, whereas delta-TCS-1 stained approximately 1/3 of such cells. In addition, the sum of the percentages of BB3+ and delta-TCS-1+ cells approximated the percentages of peripheral blood CD3+WT31- lymphocytes in seven normal donors tested. Also, in peripheral blood-derived polyclonal CD3+WT31- populations, cultured in IL-2, cells reacting with one or another mAb accounted for the whole cell population. On the other hand, only delta-TCS-1-reactive cells, but not BB3+ cells, could be detected in unfractionated as well as in CD4-8-thymocyte populations. Analysis of peripheral blood-derived CD3+WT31- clones showed that 70% of 72 clones analyzed reacted with BB3 mAb, but not with delta-TCS-1 mAb. On the other hand, delta-TCS-1 mAb stained the remaining BB3- clones. Five clones expressing medium-low amounts of CD8 antigen were BB3- delta-TCS-1+. Both types of clones lysed the Fc gamma receptor-bearing P815 target cell in the presence of anti-CD3 mAb (but not of mAb directed against HLA-DR, CD7 molecules, or TCR-alpha/beta). In this cytolytic assay, BB3 mAb induced target cell lysis only by BB3+ clones, whereas delta-TCS-1 mAb was effective only with delta-TCS-1+ clones. The CD3-associated surface molecules expressed by BB3+ or delta-TCS-1+ clones were analyzed after cell surface iodination and immunoprecipitation with the corresponding anti-TCR mAb or with anti-CD3 mAb (in digitonin-containing buffer). In SDS-PAGE, molecules immunoprecipitated from 13 BB3+ clones displayed, under nonreducing conditions, a molecular weight of 80 kD (in some cases, a minor 38-kD band could be detected). Under reducing conditions, two major components of 44 and 41 kD (and a minor component of 38 kD) were detected. On the other hand, TCR molecules immunoprecipitated from 11 different delta-TCS-1+ clones appeared as a diffuse band of 41-44 kD, both under reducing and nonreducing conditions (under non-reducing condition, an additional 38-kD band was present). Therefore, BB3+ cells express a disulphide-linked form of TCR-gamma/delta whereas delta-TCS-1+ cells express a non-disulphide-linked form.(ABSTRACT TRUNCATED AT 400 WORDS)

Antigen recognition by human T cell receptor gamma-positive lymphocytes. Specific lysis of allogeneic cells after activation in mixed lymphocyte culture

These experiments were designed to define the ability of human TCR-gamma+ cells to recognize allogeneic cells. TCR-gamma+-enriched populations were obtained by treating peripheral blood E-rosetting cells with anti-CD4 and anti-CD8 mAbs. The resulting populations were CD2+4-8- expressed variable proportions of CD3+ cells (40-90%), and did not react with the WT31 mAb, which is specific for a framework determinant of the alpha/beta heterodimer that serves as receptor for antigen on most human T lymphocytes. After mixed lymphocyte culture with irradiated allogeneic cells for 7 d and 3 additional days in rIL-2 (100 U/ml), cells underwent proliferation in three of five individuals tested. In addition, MLC-derived cells lysed 51Cr-labeled PHA-induced blasts derived from the allogeneic cells used as stimulator, but not allogeneic unrelated or autologous blast cells. No cytotoxicity against autologous or allogeneic target cells could be induced by culturing CD3+4-8-WT31- lymphocytes in MLC with irradiated autologous cells. Surface iodination of allogeneic MLC-activated CD3+4-8-WT31- cells followed by lysis in 1% digitonin and immunoprecipitation with anti-CD3 mAb indicated that the CD3-associated molecules consisted of a major 45-kD band and a minor band of 43 kD. Northern blot analysis showed that mRNA for the gamma chain was expressed at high levels, whereas mRNAs for alpha and beta chains were missing. These data support the notion that TCR-gamma rather than TCR-alpha/beta is expressed in allospecific CD3-4-8-WT31- cell populations. Clones were further derived from MLC-stimulated CD3+4-8-WT31- populations. All the seven clones studied in detail maintained the surface phenotype as well as the cytolytic pattern of the original MLC populations, thus only specific allogeneic PHA-induced blasts were lysed. NK-sensitive as well as NK-resistant tumor targets were variably susceptible to lysis; therefore, specific cytolytic activity against allogeneic cells was not necessarily linked to the expression of MHC-nonrestricted cytotoxicity against tumor cells.

CD3+4-8-WT31-(T cell receptor gamma+) cells and other unusual phenotypes are frequently detected among spontaneously interleukin 2-responsive T lymphocytes present in the joint fluid in juvenile rheumatoid arthritis. A clonal analysis

T lymphocytes (E rosetting cells) isolated from the joint fluid of four patients with juvenile rheumatoid arthritis (JRA) were first analyzed for surface antigen expression. Approximately 15% of cells were CD25+ (interleukin, IL, 2 receptor positive), in addition, a remarkable proportion of cells expressed the CD2+3- phenotype. CD3+ cells outnumbered the sum of CD4+ and CD8+ cells as well as the cells reactive with the WT31 monoclonal antibody (which recognizes a framework determinant of the alpha/beta T cell receptor). Purified T cells were cloned under culture conditions (1% phytohemagglutinin, PHA plus IL2) which allow clonal expansion of most peripheral blood T lymphocytes. Under these conditions proliferating cells ranged from 25 to 65%; clones (derived from microcultures containing 0.5 or 0.25 cells/well) were tested for cytolytic activity against P815 cells (in the presence of PHA) or against the natural killer (NK)-sensitive K562 target cells. Fifty-four percent and 73% of clones obtained from the two patients with the polyarticular form of the disease displayed cytolytic activity in the lectin-dependent assay. Cytolytic clones were 22 and 29% in the two patients with single joint involvement. About half of all cytolytic clones displayed NK-like activity. Surface antigen analysis revealed that, in addition to conventional CD3+4+8- and CD3+4-8+, a noticeable fraction of clones (50/202) displayed unusual surface phenotypes. In particular, 33/50 coexpressed CD4 and CD8 antigens; 7/50 were CD2+3-4-8- and displayed NK-like activity; 10/50 expressed CD3 but lacked both CD4 and CD8 antigen and did not react with the WT31 monoclonal antibody. In order to allow selective growth of IL2-responsive cells, T lymphocytes were also cloned directly in IL2. As much as 57% of all clones thus obtained (48/84) displayed cytolytic activity. Moreover, about half expressed unusual surface phenotypes including CD2+3-4-8-, CD3+4+8+ and CD3+4-8-WT31-. Given the accumulation at the site of the joint involvement of unusual T cells, most of which displayed cytolytic activity and were likely to represent cells activated in vivo (IL2 responsive), one may speculate that these cells may be involved in the injury process.