Alloimmunization to public HLA antigens in multi-transfused platelet recipients.

Multitransfused recipients of random donor platelet concentrates frequently form broadly-reactive human leukocyte antigen (HLA) antibodies which restrict the pool of suitable donors to those who are HLA matched with the recipient. In an effort to expand the donor pool for such patients, a retrospective analysis of the antibodies formed by alloimmunized recipients was performed taking sensitization to public HLA antigens into account. A total of 144 sera from 18 subjects was analyzed. Peak reactive sera from these patients ranged from 53 to 100 percent when tested against lymphocyte panels. When the reaction patterns of these sera were evaluated, 11 patients formed antibodies against public antigens only, three patients formed antibodies reacting exclusively with private determinants, and two patients formed antibodies reacting with both public and private antigens. The specificities in highly reactive sera from two patients could not be identified. A total of 153 lymphocyte crossmatches was performed while these patients were receiving single donor HLA-matched platelets. Forty-six positive crossmatches were obtained of which 33 occurred with donors mismatched for at least one non-crossreactive HLA antigen with the recipient. Of these, 26/33 (79 percent) positive crossmatches were predicted by the results of the serum analysis for antibodies directed against public HLA determinants. Similarly, 31/40 (78 percent) negative lymphocyte crossmatches were predictable on the basis of the serum analysis. It is concluded that "multispecific" lymphocytotoxic antibodies formed by multitransfused recipients of platelet concentrates, are often directed against one or a few public HLA determinants.(ABSTRACT TRUNCATED AT 250 WORDS)