Can Anti HLA‐A and ‐B Antibodies Inhibit the MLC Test?

Eleven lymphocytotoxic pregnancy sera were tested for inhibition in the MLC test. Responder inhibition and stimulator inhibition were analyzed separately by using cells from the serum producer as stimulator and responder respectively. Only three sera showed inhibitionof responder function, whereas all sera showed inhibition of stimulator function. The specificity of the latter inhibition was at least in part attributable to antibodies directed to specificities other than B-cell specificities (presumed to be coded for in the HLA-D region). This was deduced from the fact that platelet eluates devoid of anti B-cell antibodies effectively inhibited in MLC.