Platelet absorption on the test tray (PATT): a rapid method for the screening of HLA class II antibodies using the two-colour fluorescence method.

Several strategies have been proposed for the screening of alloantisera towards HLA class II antigens. Most often the absorption of the sera with platelets is required in order to remove their anti-HLA-A, B, C activity. We have developed a simple micromethod for platelet absorption of sera: platelet absorption on the test tray (PATT); 0.5 microliter of platelet suspension is incubated with 0.5 microliter of the serum to be absorbed in the same tray which is subsequently used for the microlymphocytotoxicity by the two-colour fluorescence method. This technique is proved to be almost as efficient as classical absorption procedures: out of 44 anti-HLA-A, B sera the T-cell activity is completely removed in 43 by a classical procedure as compared to 41 by PATT; only 8% discrepancies were found among 394 reactions. PATT was then used for anti-B lymphocyte screening in 419 anti-HLA-A, B sera; 4% of the sera remained cytotoxic towards T and B lymphocytes while 35% reacted only with B cells, several of them being DR specific. PATT can also be useful for T/B lymphocyte differential cross-matches before kidney transplantation. The method is now routinely used in our laboratory for anti-HLA class II antibody screening.