Dual T cell receptor beta chain expression on human T lymphocytes.

Allelic exclusion of lymphocyte antigen receptor chains has been hypothesized as a mechanism developed by the immune system to ensure efficient lymphocyte repertoire selection and tight control of lymphocyte specificity. It was effectively shown to be operative for both the immunoglobulin (Ig) and the T cell receptor (TCR) beta chain genes. Our present observations suggest that close to 1% of human T lymphocytes escape this allelic control, and express two surface TCR beta chains with distinct superantigenic reactivities. Since this high frequency of dual beta chain expressors did not result in any dramatic immune dysregulations, these results question the need for a mechanism ensuring clonal monospecificity through allelic exclusion.

Surface expression of functional T cell receptor chains formed by interlocus recombination on human T lymphocytes.

Structural diversity of lymphocyte antigen receptors (the immunoglobulin [Ig] of B cells and the alpha/beta or gamma/delta T cell receptor [TCR] of T cells) is generated through somatic rearrangements of V, D, and J gene segments. Classically, these recombination events involve gene segments from the same Ig or TCR locus. However, occurrence of "trans" rearrangements between distinct loci has also been described, although in no instances was the surface expression of the corresponding protein under normal physiological conditions demonstrated. Here we show that hybrid TCR genes generated by trans rearrangement between V gamma and (D) J beta elements are translated into functional antigen receptor chains, paired with TCR alpha chains. Like classical alpha/beta T cells, cells expressing these hybrid TCR chains express either CD4 or CD8 coreceptors and are frequently alloreactive. These results have several implications in terms of T cell repertoire selection and relationships between TCR structure and specificity. First, they suggest that TCR alloreactivity is determined by the repertoire selection processes operating during lymphocyte development rather than by structural features specific to V alpha V beta regions. Second, they suggest the existence of close structural relationships between gamma/delta and alpha/beta TCR and more particularly, between V gamma and V beta regions. Finally, since a significant fraction of PBL (at least 1/10(4)) expressed hybrid TCR chains on their surface, these observations indicate that trans rearrangements significantly contribute to the combinatorial diversification of the peripheral immune repertoire.

T cell response to Epstein-Barr virus transactivators in chronic rheumatoid arthritis.

Rheumatoid arthritis is a multistep disorder associated with autoimmune features of yet unknown etiology. Implication of viruses such as Epstein-Barr virus (EBV) in rheumatoid arthritis pathogenesis has been suspected on the basis of several indirect observations, but thus far, a direct link between EBV and rheumatoid arthritis has not been provided. Here we show that a large fraction of T cells infiltrating affected joints from a patient with chronic rheumatoid arthritis recognizes two EBV transactivators (BZLF1 and BMLF1) in a major histocompatibility complex-restricted fashion. Responses to these EBV antigens by synovial lymphocytes from several other chronic rheumatoid arthritis patients were readily detectable. Thus these results suggest a direct contribution of EBV to chronic rheumatoid arthritis pathogenesis. They also demonstrate for the first time the occurrence of T cell responses against EBV transactivating factors, which might be central in the control of virus reactivation.

Surface expression of two distinct functional antigen receptors on human gamma delta T cells.

Lymphocytes recognize antigens with highly variable heterodimeric surface receptors. Although four distinct antigen receptors could in principle be produced by any lymphocyte, only one functional combination of receptor chains has thus far been found expressed on their surface. Examination of human gamma delta T cells revealed a population that violated this rule by expressing on their surface two distinct functional gamma delta T cell receptors (TCRs) that used different TCR gamma gene alleles. Thus, current models for T cell clonal selection may need modification, and a possible escape mechanism for autoreactive TCRs is suggested.

Stimulation of human gamma delta T cells by nonpeptidic mycobacterial ligands.

Most human peripheral blood gamma delta T lymphocytes respond to hitherto unidentified mycobacterial antigens. Four ligands from Mycobacterium tuberculosis strain H37Rv that stimulated proliferation of a major human gamma delta T cell subset were isolated and partially characterized. One of these ligands, TUBag4, is a 5' triphosphorylated thymidine-containing compound, to which the three other stimulatory molecules are structurally related. These findings support the hypothesis that some gamma delta T cells recognize nonpeptidic ligands.

T lymphocyte cloning from rejected human kidney allografts. Growth frequency and functional/phenotypic analysis.

Mechanically harvested lymphocytes invading an irreversibly rejected human kidney allograft were seeded at limiting dilution to calculate the frequency of growing precursors. Optimal growth frequency (1/13) was obtained when Epstein-Barr virus (EBV)-transformed donor B lymphocytes were used as stimulators (D-BLCL) in the presence of interleukin 2 (IL-2). The 55 clones analyzed were all T11+ and T3+, and all expressed DR antigens (45% were T8+ and 55% T4+). Only one clone had a double-labeled (T4+ T8+) surface. All cells proliferated significantly against D-BLCL, although T4+ clones had a significantly shorter average doubling time than T8+ clones. Nearly all T8+ clones were specifically cytotoxic for D-BLCL, while both T4 and T8 did not react against K562, autologous EBV-BLCL, and third-party EBV-BLCL. Detectable IL-2 was found in the culture supernatants of only a minority of clones (all T4+).

TCRBV23 specificity of two monoclonal antibodies revealed by a panel of human V beta chains expressed in mouse cells.

Two monoclonal antibodies, HUT78#1 and HUT78#7, were made against the T cell receptor of the T leukemia line HUT78. Their specificity was originally determined as TCRBV1S1 (V beta 1), and they have been used as such in repertoire studies (Rebai et al., 1994, Proc. Natl. Acad. Sci. USA 91, 1529). Here, we report their characterization using a large panel of mouse T cell transfectants expressing various human T cell receptor beta chains at their surface. These transfectants revealed that the true specificity of both monoclonal antibodies was for TCRBV23S1 (V beta 23), a result that was confirmed by several other techniques. We show that the original determination as a V beta 1 specificity was due to a crossreactive oligonucleotide used to type the immunizing cell line. The oligonucleotide amplified the V beta 1 as well as the closely related V beta 23 sequence, while the antibodies, by contrast, react exclusively with the beta chain encoded by the V beta 23 subfamily of the T cell receptor. Both antibodies seem to have identical specificities. These antibodies will be useful for the detection of a new subset of human lymphocytes since, to date, no other reagent with reactivity for the V beta 23 chain of the human T cell receptor has been described so far.

Preparative two-step purification of human IL-2 by HPLC and hydrophobic affinity chromatography.

Interleukin 2 (IL-2) has been purified by a protocol using gel filtration high performance liquid chromatography (HPLC) and hydrophobic affinity chromatography with blue-trisacryl M. Peripheral blood lymphocytes or tonsillar lymphocytes were stimulated with phytohemagglutinin (PHA). Serum free conditioned medium (CM) containing IL-2, other lymphokines and residual PHA molecules was analyzed after 3 variations of ammonium sulfate (AS) precipitation: (1) precipitation of CM with 50% AS yielded a precipitate containing most of the residual PHA but also a fraction of IL-2. (2) Precipitation with direct 80% AS of crude CM yielded both IL-2 and residual PHA. (3) A double step procedure (50% AS followed by 80% AS) yielded a precipitate containing IL-2 but free of residual lectin. HPLC purification of these various AS-precipitated materials or of lyophilized crude CM yielded 2 peaks with mitogenic activity as assayed with the CTLL2 murine clone or IL-2-dependent human Con A-stimulated lymphoblasts. IFN was easily separated from IL-2 and PHA, but BCGF still copurified with IL-2. Peak I (25 kDa) was enriched 400-fold for IL-2 while peak II (68 kDa) contained the residual PHA. The IL-2-containing fractions eluted from HPLC were further purified by blue-trisacryl M chromatography. The IL-2 eluted with 0.4 M NaCl. The entire protocol (HPLC followed by blue-trisacryl) led routinely to 8000-fold IL-2 enrichment. Preparative HPLC directly applied to lyophilized crude (CM) enriched IL-2 activity 400-fold with yield averaging 60% of the IL-2 input. The final material was free from interferon and IL-1, but BCGF still copurified with IL-2. The 2-step purified material (HPLC and blue-trisacryl) gave 2 bands in SDS-PAGE both of which contained IL-2.

Structural analysis of gamma delta TCR using a novel set of TCR gamma and delta chain-specific monoclonal antibodies generated against soluble gamma delta TCR. Evidence for a specific conformation adopted by the J delta 2 region and for a V delta 1 polymorphism.

We recently showed that secretion of non-chimeric disulfide-linked human gamma delta TCR ('soluble' TCR, sTCR) comprising V gamma 9 and V delta 2 regions could be achieved by simply introducing translational termination codons upstream from the sequences encoding TCR transmembrane region. Here we extended these findings by demonstrating efficient secretion and heterodimerization of gamma delta sTCR comprising V gamma 8, V delta 1 and V delta 3 regions, obtained via the same strategy. After immunization against immunoaffinity-purified soluble TCR, several hundreds of TCR-specific monoclonal antibodies (mAb) were generated, which fell in at least seven groups. One set of mAb was directed against a V gamma 8-specific epitope. Strikingly, despite the high degree of sequence homology between V gamma 8 and other V gamma I domains, none of these mAb were crossreactive with other members of the V gamma I family. Three other sets of mAbs were shown to recognize delta chains comprising V delta 1, V delta 2 and V delta 3 regions respectively, regardless of their junctional sequence or of the gamma chain to which they were paired. Among the V delta 1-specific mAb, some specifically recognized V delta 1D delta J delta C delta chains while others reacted with both V delta 1 D delta J delta C delta and V delta 1J alpha C alpha chains, which suggested V domain conformational alterations induced by the C region. Moreover, reactivity of one V delta 1-specific mAb (#R6.11) was affected by a polymorphic residue located on the predicted CDR4 loop of the V delta region. Two delta chain-specific mAb (#178 and #515) showed a highly unusual reactivity, which was negatively affected by particular V delta and J delta sequences: (i) mAb #515 and #178 recognized all TCR delta chains except those comprising V delta 1 or V delta 2 regions, respectively and (ii) within TCR delta chains carrying 'permissive' V delta regions, none of those comprising the J delta 2 region were recognized by #515 and/or #178 mAbs, which suggested a highly specific conformation adopted by this particular J delta sequence. Apart from its usefulness in TCR structural studies, this novel set of mAb represents an important tool for the characterization and isolation of gamma delta T cells expressing particular combinations of V gamma/V delta regions and for analysis of V alpha/V delta usage by alpha beta T cells. Moreover, since our present data strongly suggest that gamma delta TCR are easier to obtain in a soluble form than alpha beta TCR, an efficient strategy for the generation of V alpha region-specific mAb might be to immunize with chimeric gamma delta sTCR comprising particular V alpha regions.

The effects of cyclosporine on HILDA/LIF gene expression in human T cells.

We examined the effect of cyclosporine on HILDA/LIF gene expression in alloreactive human T lymphocyte clones (ATLCs) 2B11 and 2F7 obtained from cells infiltrating a rejected human kidney graft. Both ATLCs were stimulated either by the specific antigen or by PMA + calcium ionophore in the presence of various concentrations of CsA (10-500 ng/ml). Inhibition of HILDA/LIF gene expression was analyzed at the protein level using a proliferative assay on the HILDA/LIF-dependent Da-1a cell line and by RNA blotting using a specific probe. Without CsA, the kinetics of mRNA accumulation for both ATLCs peaked at 5 and 10 hr, respectively, after mitogenic and antigenic stimulations. HILDA/LIF activity peaked at 24 and 72 hr, respectively, after mitogenic and antigenic stimulation in supernatants from both ATLCs and decreased thereafter. Subsequent experiments with CsA were thus performed at these time points. Our results show that HILDA/LIF mRNA accumulation and protein secretion in 2B11 and 2F7 clones were strongly inhibited in a dose-dependent manner by CsA, in both stimulation conditions. Maximal inhibition of HILDA/LIF transcripts and protein secretion (60-90%) was observed within the range of 75-500 ng/ml CsA.

Systematic transfusion in hemodialyzed patients awaiting grafts: kinetics of anti-t and b lymphocyte immunization and its incidence on graft function.

Since June 1977, a systematic blood transfusion (BT) policy (160 ml of leukocyte-poor washed erythrocytes given every 6 months) has been applied to 126 hemodialyzed patients awaiting a first kidney graft. Only patients who had anti-T or B lymphocyte (T or BLY) antibodies (Ab) killing fewer than 10 or 20% of the panel cells, respectively, entered the protocol. Screening of anti-T and BLY was performed 8, 15, and 21 days after each BT. Patients were removed from the protocol if they developed Ab against more than 10 or 20% of the T or BLY panel cells. The cumulative immunization (all Ab types) averaged 90% after four BTs. Anti-BLY (63%) were more frequent than anti-TLY (49%) after for BTs. No anti-HLA-DR specificity could be attributed to the anti-BLY, whereas 20% of the anti-TLY displayed a particular anti-HLA-A,B specificity. Patients that had had BTs or pregnancies before entering the protocol had a higher degree of immunization. The kinetics of the anti-B or TLY pattern differed greatly both at the level of their detection after 8, 15, and 21 days following one BT and in their development after repeated BTs. Forty-three patients received transplants at various stages of the protocol. Recipients grafted without Ab had the best graft outcome (87 versus 66 actuarial percentage at 3 months), even though their HLA (A,B and DR) matching was inferior. There was no significant difference in recipients who had different subgroups of Ab. These data indicate that immunization is very high even after a few BTs when careful controls are performed and they suggest that BTs do not act via active enhancement.

T cell colony-forming frequency of mononucleated cells extracted from rejected human kidney transplants. Functional and phenotypic studies of the colonies.

One line of investigation of cellular events leading to rejection of an allograft has been to collect the cells infiltrating the rejected allograft and to subject them to in vitro functional and cell marker analysis. Outlined in this article is a description of the limiting dilution analysis technique applied to mechanically disrupted cells obtained from three different rejected human kidney allografts and a phenotypic cell surface marker, as well as a functional study of the progeny of such cells at a clonal level. Of the harvested cells, 65% were T11+, 58% were OKT8+, and 14% were OKT4+. The frequencies of colony forming cells (CFC) were assessed in liquid medium supplemented with lectin-free purified IL-2 (selecting in vivo activated cells) or with IL-2 plus PHA. The CFC frequencies ranged from 1/777 to 1/120 cells plated and from 1/250 to 1/90 cells plated in, respectively, IL-2 and IL-2 plus PHA. Only colonies with a probability of monoclonality more than 80% were further expanded in the presence of lectin-free IL-2. Among 31 colonies grown in the presence of IL-2 alone, all colony-cells were OKT11+, 4/31 were T4+T8-, 24/31 T4-T8+--and, finally, 3/31 were T4+T8+. On the other hand, 122 colonies grown in the presence of IL-2 plus PHA were also all OKT11+, but 47/122 were T4+T8-, and 62/122 were T4-T8+. In addition, expression of DR molecules was highly variable from colony to colony. Significant antidonor cytotoxicity was recorded in 24 colonies, most of them expressing T8 molecules at their surface. Moreover cytotoxic antidonor colonies seemed to recognize an antigen determinant different from the known HLA incompatibilities between donor and recipient. In three long-term-cultured colonies, we noticed a shift in surface marker: from the expression of T8 to either the coexpression of T4 or the loss of the T8 to the sole expression of the T4 molecules. This methodology is a step forward in the elaboration of techniques for determining the relationships between the surface marker identity and the immune function of cells activated in vivo, which are found in a rejected human kidney.

Characterization of CMVpp65-specific CD8+ T lymphocytes using MHC tetramers in kidney transplant patients and healthy participants.

BACKGROUND: Cytomegalovirus (CMV) is a ubiquitous herpesvirus that infects 50-90% of individuals in different populations. After primary infection, the virus persists latently in myeloid cells under the control of specific T-cells. Reactivation of CMV infection may cause lethal organ dysfunction and is frequently seen in immunosuppressed individuals. CD8+ cytotoxic T-cells (CTL) have a primary role in suppressing CMV reactivation, and the dominating CTL response is directed against pp65. METHODS: MHC tetramers, that is, complexes between HLA class I (or class II) molecules and antigenic peptides conjugated to fluorochromes allow the direct visualization of antigen-specific receptor-carrying T-cells using flow cytometry. We constructed a novel MHC tetramer for identification of CMVpp65-specific CD8+ T-cells using HLA-A2 molecules folded with the immunodominant NLVPMVATV peptide. RESULTS: The A2/pp65 tetramer specifically stained CMV-directed T-cell lines, and sorted cells showed CMV-specific cytotoxicity. High proportions (0.1-9%) of the CD8+ T-cells were A2/pp65 tetramer+ in healthy HLA-A2+ CMV carriers and in immunosuppressed kidney transplant patients with latent infection. Patients with reactivated CMV infection exhibited up to 15% A2/pp65 tetramer+ cells, which seemed to correlate with CMV load over time. A2/pp65 tetramer+ cells expressed T-cell activation markers. CONCLUSIONS: The construction of a novel A2/pp65 MHC tetramer enabled the design of a rapid and precise flow cytometric method allowing quantitative and qualitative analysis of CMV-specific T-cells. The number of A2/pp65 tetramer binding CTLs in blood may prove to be clinically relevant in assessing the immune response to CMV.

Epitopic analysis of HLA DR molecule expression on alloreactive T-cell clones.

The expression of HLA-DR epitopes, recognized by a set of anti-DR MoAbs clustered into four groups according to immunochemical studies, was analyzed at the surface of in vivo-sensitized alloreactive T-cell clones derived from a rejected kidney allograft and on the autologous B lymphoblastoid cell line (BLCL). Although no clear-cut differences were noted between T cells themselves and T cells vs BLCL in the relative expression of most of the DR epitopes studied (D1.12, BT2/9, VI.15C, 135, 206, 141, BM50), relative and absolute expression of one DR epitope (BMMag8) was strikingly higher on autologous BLCL than on T-cell clones. Moreover, the absolute expression of DR epitopes was heterogeneous among T cells. Such differences could not be explained either by T-cell activation level (assessed by IL2 receptor or transferrin receptor expressions) or by differences in time kinetics expression. In other tests, anti-DR MoAbs were assayed for their ability to block cytotoxic activity of several T-cell clones directed against DR allospecificities. Each T-cell clone showed distinct inhibition patterns. By such analysis, it was possible to define several groups of epitopes not always identical to those defined by immunochemical studies. Finally, analysis of the ability of MoAb to specifically block cytotoxicity mediated by 2 anti-DRw8 T-cell clones at the target level allowed precise epitopic study of polymorphic DRw8 determinants recognized by these cells, in this case borne by a single DR alpha/beta heterodimer.

Simultaneous transcription of eleven cytokines in human alloreactive T lymphocyte clones after stimulation by phorbol ester and A23187.

Human alloreactive T lymphocyte clones derived from cells invading a rejected kidney allograft, were analyzed for their ability to transcribe eleven cytokine genes under phorbol ester (PMA) plus calcium ionophore (CaI A 23187) stimulation. In addition to the positive signal previously obtained for IL-2 transcripts, strong specific patterns were seen with cytoplasmic dot hybridizations for IFN gamma and GM-CSF mRNAs in all the 17 clones screened. For the remaining transcripts (IL-3, IL-4, IL-5, IL-6, TNF alpha, LT, M-CSF and HILDA/LIF), these techniques proved to be inadequate. Northern-blots were therefore performed on three clones exhibiting different phenotypes (CD4+ CD8- non cytotoxic, CD4+ CD8- cytotoxic and CD4- CD8+ cytotoxic). Positive specific signal with the eleven probes could be obtained. Nevertheless, the IL-6 message was found only in the helper clone and the TNF alpha transcript appeared at a later time point compared to the other cytokine messages (its maximum expression was observed around 24 hours post-stimulation). In conclusion, we demonstrate that under PMA+CaI activation, one clone is able to simultaneously transcribe at least eleven lymphokine genes. Except, perhaps for IL-6, the pattern of lymphokine transcription did not permit us to distinguish between different lymphocyte subsets.