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Biomedical subjects

J A Smit

Publications and source records attributed to J A Smit.

At least 73 records · Page 4Linked to original sources
PubMed1978

Active enhancement in the primate by bone marrow I. Ia-like determinants on nucleated bone marrow cells.

This study investigates the possibility that the active enhancing properties of bone marrow (BM) cells may be related to Ia-like determinants on their surface membranes. Less chromium was released on a cell per cell basis from nucleated baboon BM cells used as targets in complement-dependent cytotoxicity than from labelled lymph node lymphocytes. On the other hand, BM cells stimulated allogeneic lymphocytes in culture more vigorously than lymph node lymphocytes. BM cells with lymphocyte-activating properties could be enriched by fractionation on a discontinous bovine serum albumin gradietnt. BM cells responded poorly to allogeneic cell stimulation in mixed culture. Platelet absorption studies of an alloantiserum supported the conclusion that nucleated BM cells, and particularly BM fractions collected from the less dense interfaces of a bovine serum albumin gradient, express relatively more lymphocyte-activating or Ia-like determinants than "serologically defined" determinants.

Absorption↗
PubMed1976

Cross-matching assays of cell-mediated immunity for transplant patients.

Assays of cell-mediated immunity before transplantation were performed on 34 patients who were defined as being at high risk by the presence of preformed lymphocytotoxic antibodies and/or HL-A incompatibilities at FOUR locus. Assays for cell-mediated lympholysis type I (cml I) were performed in donor serum, and for CML II in recipient serum, to assess the possible effect of blocking factors in the patients' sera. A positive (greater than 5% specific Cr release) and in particular a greater than 10% Cr release correlated strongly with graft rejection. The correlation between CML II and graft survival was unimpressive. No clinically beneficial blocking factor was demonstrable in the patients's sera in that 5 of 6 patients with a positive CML I but a negative CML II rejected their grafts. Conversely, 6 of 8 patients with a positive CML II and a negative CML I had excellent long-term courses. The use of CML I assay in the selection of grafts for patients at high risk is recommended.

Cadaver↗
PubMed1975

Detergent solubilisation of baboon histocompatibility antigens and their use in prolonging liver allograft survival.

Histocompatibility antigens have been solubilised from baboon spleen cell membranes by brief exposure to sodium deoxycholate (DOC). Preparations contained a high molecular weight species (DOCH-Ag) excluded by Sephadex G-200, and a low molecular weight species (DOCL-Ag) which eluted in the included fraction (molecular weight 46,000). The low molecular weight antigen was stable and was not sedimented by high speed centrifugation even after dialysis against a low molar salt solution. It elicited a delayed-type hypersensitivity response in sensitised baboons but not in normal animals. DOCL-Ag cultured in vitro with sensitised allogeneic lymphocytes produced a 1.3- to 24.9-fold stimulation, whereas when cultured with normal lymphocytes the maximum stimulation index was 2. Intravenous administration of donor DOCL-Ag (2 mg/kg) at the time of transplantation and without additional immunosuppression significantly prolonged the mean survival time of baboon liver allografts. The same treatment with donor DOCH-Ag did not prolong graft survival.

Animals↗
PubMed1975

Prolongation of liver allograft survival by donor-specific soluble transplantation antigens and antigen-antibody complexes.

Soluble transplantation antigens were prepared from chacma baboon spleen cell membranes by a modified 3 M KCl technique. The extracts were soluble according to usually accepted criteria. Molecular weight was 37,700 daltons. Antigenicity was confirmed by inhibition of cytotoxicity of alloantibody. The antigens stimulated sensitized lymphocytes in culture but failed to stimulate unsensitized lymphocytes. Antigen-antibody complexes were assembled in vitro in the regions of equivalence and marked antigen excess. Administration of a single dose of soluble donor antigen at the time of orthotopic liver allotransplantation prolonged graft survival significantly. Concomitant administration of a polyspecific alloantibody, previously shown to prolong baboon liver allograft survival, abrogated the graft prolongation produced by the antigen or antibody given alone. When the administration of the soluble antigen was preceded by a dose of cyclophosphamide (20 mg/kg), graft prolongation was slightly curtailed. Antecedent administration of azathioprine and prednisolone for 3 days seemed to render the antigen immunogenic in that liver allograft rejection was accelerated. Antigen-antibody complexes at equivalence prolonged liver allograft survival beyond that seen with antigen alone, but complexes in marked antigen excess were immunogenic, inasmuch as graft survival was not prolonged and the histological features were those of accelerated rejection.

Animals↗