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R I Lechler

Publications and source records attributed to R I Lechler.

159 records · Page 9Linked to original sources
PubMed1985

"Exon-shuffling" maps control of antibody- and T-cell-recognition sites to the NH2-terminal domain of the class II major histocompatibility polypeptide A beta.

To investigate the role of the highly polymorphic amino-terminal (beta 1) domain of the class II major histocompatibility polypeptide A beta during recognition by T cells and antibodies, "exon-shuffling" was carried out between genomic recombinant DNA clones of Ak beta and Ad beta to generate a hybrid gene containing Ak beta exons for the amino-terminal domain followed by the Ad beta exons for the remainder of the molecule. L-cell gene transfectants expressing this hybrid A beta gene in combination with Ak alpha were compared to L cells expressing wild-type Ak beta Ak alpha dimers in tests of antigen-presentation to T-cell clones and hybridomas and for staining by a panel of anti-I-Ak-specific monoclonal antibodies. These antibodies were also tested for their reactivity with a B-lymphoma transfectant expressing Ak beta in the absence of Ak alpha. The results showed no qualitative differences in either T-cell or antibody-mediated recognition of I-Ak molecules containing either the exon-shuffled or wildtype Ak beta. Together with the data involving the B cell transfectant expressing only Ak beta, these results map control of the A beta contribution to the immunologically relevant determinants of I-Ak to the highly polymorphic amino-terminal domain and indicate little, if any, contribution to allele-specific recognition by amino acid sequence variations in the remaining portions of the A beta polypeptide.

Alleles↗
PubMed1985

Qualitative and quantitative studies of antigen-presenting cell function by using I-A-expressing L cells.

I-A-expressing transfected murine L cells were analyzed as model antigen-presenting cells. Four features of accessory cell function were explored: antigen processing, interaction with accessory molecules (LFA-1, L3T4), influence of Ia density, and ability to stimulate resting, unprimed T lymphocytes. I-A+ L cells could present complex protein antigens to a variety of T cell hybridomas and clones. Paraformaldehyde fixation before but not subsequent to antigen exposure rendered I-A+ L cells unable to present intact antigen. These results are consistent with earlier studies that made use of these methods to inhibit "processing" by conventional antigen-presenting cells. The ability of anti-L3T4 antibody to inhibit T cell activation was the same for either B lymphoma or L cell antigen-presenting cells. In striking contrast, anti-LFA-1 antibody, which totally blocked B lymphoma-induced responses, had no effect on L cell antigen presentation, measured as interleukin 2 (IL 2) release by T hybridomas, proliferation, IL 2 release, or IL 2 receptor upregulation by a T cell clone. I-A+ L cell transfectants were found to have a stable level of membrane I-A and I-A mRNA, even after exposure to interferon-gamma-containing T cell supernatants. In agreement with earlier reports, a proportional relationship between the (Ia) X (Ag) product and T cell response was found for medium or bright I-A+ cells. However, dull I-A+ cells had a disproportionately low stimulatory capacity, suggesting that there may be a threshold density of Ia per antigen-presenting cell necessary for effective T cell stimulation. Finally, I-A-bearing L cells were shown to trigger low, but reproducible primary allogeneic mixed lymphocyte responses with the use of purified responder T cells, indicating that they are capable of triggering even resting T cells. These studies confirm the importance of antigen processing and I-A density in antigen-presenting cell function, but raise questions about the postulated role of the LFA-1 accessory molecule in T cell-antigen-presenting cell interaction. They also illustrate the utility of the L cell transfection model for analysis and dissection of antigen-presenting cell function.

Animals↗
PubMed1982

Immunogenicity of retransplanted rat kidney allografts. Effect of inducing chimerism in the first recipient and quantitative studies on immunosuppression of the second recipient.

It has been previously shown that long surviving, enhanced (AS X AUG)F1 rat kidneys residing in a primary AS recipient are not acutely rejected if transferred into a second AS recipient. The reduced immunogenicity of the retransplanted graft was attributed to a depletion of incompatible passenger cells. It is shown here that if the primary AS recipient is made chimeric by x irradiation and injection of (AS X AUG)F1 bone marrow cells, transfer of the long surviving, enhanced graft into a second AS recipient provokes acute graft rejection comparable to that observed when normal (AS X AUG)F1 kidneys are transplanted into untreated AS recipients. Transplantation of passenger cell-depleted AUG kidneys into AS recipients leads to graft rejection, with a median survival time of 22 d. Treatment of these recipients with as little as 1.5 mg/kg cyclophosphamide for 14 d induces prolonged graft survival. By contrast, five times as much cyclophosphamide treatment is required to induce prolonged survival of normal AUG kidneys (i.e., containing incompatible passenger cells) transplanted to AS recipients. These results confirm that the major alloimmunogenic stimulus of rat kidney grafts is provided by the incompatible passenger cells.

Animals↗
PubMed1982

Restoration of immunogenicity to passenger cell-depleted kidney allografts by the addition of donor strain dendritic cells.

The immunogenicity of long-surviving, enhanced (AS X AUG)F1 renal allografts retransplanted into secondary AS recipients was restored by the injection of small numbers of donor strain dendritic cells derived from afferent lymph. Whereas 1 X 10(4) to 5 X 10(4) dendritic cells were able to trigger an acute rejection response, neither the passenger volume of donor strain blood nor 5 X 10(6) T or B lymphocytes were able to do so, thereby demonstrating more than a 100-fold difference in immunogenic potency. It is concluded that intrarenal dendritic cells provide the major immunogenic stimulus of a kidney allograft. These results suggest that the antigenic strength of major histocompatibility complex-incompatible tissue correlates with the content of donor strain dendritic cells. They also provide further evidence that antigens of the major histocompatibility complex behave like conventional antigens unless they are on the surface of allogeneic dendritic cells.

Animals↗