HLA-restricted lymphoproliferative responses to MN blood group determinants

It is well established that strong proliferative responses in mixed lymphocyte culture (MLC)1 are controlled by gene products of the HLA-D locus, but stimulation between HLA-D identical individuals does occur and may partly be due to differences at the HLA-A, or HLA-B loci. However, many unrelated individuals who type identically for HLA-A, -B, -C, and -D/DR determinants have also been shown to be mutually stimulatory. The development of the primed lymphocyte test (PLT) provided a powerful tool in the identification of these non-HLA loci2–9. Using this test, we show here that significant HLA-restricted proliferative responses occurred in association with M or N blood group antigens.