IEF analysis of HLA molecules immunoprecipitated by putative anti-class I-like alloantisera

Two human alloantisera, previously described as possibly detecting new beta 2-microglobulin associated proteins, selectively expressed on HLA-A2 and HLA-A1 phytohaemagglutinin (PHA)-activated lymphocytes, immunoprecipitated only molecules with the same isoelectric point as HLA-A1 and A2 products. This result suggests that the selected alloantisera do not react with the products of an HLA class I locus different from ABC but probably recognize a new epitope arising on HLA-A molecules upon conformational changes consequent to cell activation.