ALLOANTIGENS DERIVED FROM STIMULATOR CELLS AND BOUND ONTO MLC-ACTIVATED RAT T-LYMPHOBLASTS

Rat T lymphocytes were activated in MLC (mixed leucocyte culture) against allogeneic stimulator cells. A few percent of such T blasts could be shown to carry IgM on their surface when a mixture of T and B lymphocytes was used as responder cells. The immunoglobulin was absent when purified T lymphocytes served as responders, A large proportion of MLC T lymphoblasts could be shown to carry stimulator alloantigens on their surface. These antigens were demonstrated (a) by indirect immunofluorescence using anti‐stimulator alloantibody and FITC (fluorescein isothiocyanate Isomer I)‐labelled F(ab)2 fragments of rabbit anti‐rat Ig; (b) by autoradiography after internal labelling of stimulator cells. which showed the transfer of label from stimulator to responder cells. For biochemical analysis T blasts were restimulated with internally labelled allogeneic or syngeneic stimulator cells, and bound radiolabelled stimulator alloantigens were analysed on SDS‐PAGE (sodium lauryl sulphate polyacrylamide gel electrophoresis). The results suggest that intact SD antigens with a molecular weight of 45,000 daltons and LD determinants with a molecular weight of 34,000 daltons derived from stimulator cells are found on MLC T blasts. No evidence of binding of the 27,000‐dalton la chain to T blasts was found. Possible arrangements of these molecules on the responder blasts is discussed. Copyright © 1979, Wiley Blackwell. All rights reserved