Low responsiveness in MLC induced by certain HLA--A antigens on the stimulator cells.

An individual, BK, repeatedly gave typing responses against homozygous typing cells representing more than two HLA--D antigens. Family studies showed that she had inherited the HLA--Dw2 and Dw7 determinants, in agreement with results from primed lymphocyte typing. The HLA--A, B, C types of the stimulators giving rise to unexpected typing responses all involved the HLA--A1, A3 or A11 antigens. The hypothesis of this specificity in low-responsiveness was confirmed in the independent stimulator sample provided by the 7th workshop homozygous typing cell panel. The same pattern was observed when BK was tested as a responder towards related and unrelated heterozygous stimulators. Furthermore, in three-cell experiments it was found that BK cells were able to suppress the response to the Dw-identical individual, BS, towards stimulators carrying HLA--A1, A3, or A11. This effect of BK's cells appeared to be radiosensitive. We were not able to demonstrate suppressive supernatant factors in the relevant cultures, neither were we able to find circulating cytotoxic cells by the direct CML-technique, nor an accelerated cytotoxic response by the indirect CML-technique against targets carrying HLA--A1 or A3. This is the first demonstration of induction of suppressor cells in MLC by HLA--A, B, C antigens in the stimulator cells.