Retention of HLA Antigens on Previously Frozen Human Platelets

Recent technical achievements allow satisfactory cryopreservation of human platelets that, after thawing and washing, maintain functional viability for therapeutic use. We have now demonstrated that such previously frozen platelets retain full HLA antigenic activity in spite of the combination of freezing, thawing, and washing procedures and the presence of the surface‐active cryopreservative DMSO. Platelets stored at 4 C without DMSO and previously frozen platelets from the same donors were tested in parallel for quantitative expression of HLA antigens. In all cases, the previously frozen platelets were quantitatively equal or superior to the platelets stored at 4 C with regard to their capacity to specifically reduce the HLA antibody activities of selected typing sera against a panel of antigen‐positive lymphocytes. 1980 AABB