Antigen Report: HLA-A2

A2, one of the first HLA antigens to be recognized, was split early on into A2 and A28. Although at the time of the 1980 workshop it seemed to be a well-characterised entity, even then nonserological techniques (cytotoxic T cells) were beginning to show that there are variants of A2. At the present workshop A2, as studied with classic antisera, remains clearly defined. Among seven antisera, which primarily reacted with A2 positive cells, there were five with Q-scores of over 9. These gave results which were about as good as one could hope for. They detected some 99% of cells designated A2 by the submitting laboratories and gave 0–3% of extra reactions, a proportion of which may have been due to carry- over as judged by collateral evidence (for example, the first A2 antiserum after the A1 sera had a tail of A1 reactions). The assignment of A2 to specific cells by the submitting laboratories was in almost perfect agreement with the subsequent computer assignment; it was the antigen with the highest level of concordance in this regard (r=0.99).