SECONDARY MOUSE MIXED LYMPHOCYTE-REACTION (MLR) INVITRO - CORRELATION BETWEEN PRIMED CELLS REACTIVITY AND SEROLOGICAL TYPING FOR IA SPECIFICITIES

B10.M (H-2f) spleen lymphocytes were cultured for 14 days with X-irradiated B10.P (H-2p) lymphocytes. These primed cells were then tested for their capacity to respond to a secondary stimulation induced by a panel of mouse cells carrying different H-2 haplotypes. The third-party cells induced various degrees of proliferation which could be expressed as a percentage of the proliferation induced by the primary stimulating strain (relative response = RR) and could then be classified according to the RR. Anti-Ia antibodies present in a B10.M anti-B10.P serum were studied by the dye exclusion lymphocytotoxicity technique (LCT) against the same panel, after absorption of H-2K, D antibodies on B10.P platelets. The strain panel could then be classified according to the LCT titers of the absorbed immune serum. A significant correlation (r=0.96, P<0.01) was found between both classifications. According to the Ia chart, the public specificities involved were Ia.6, 7, and 13, but these did not fully explain either the primed cell reactivity or the LCT results. An unexpected crossreactivity was observed between B10.P and B10. Absorption-elution experiments with A.TH anti-A.TL serum demonstrated that B10 and B10.P share the Ia.3 antigen. These results indicate that the structure(s) recognized by the primed lymphocytes is the Ia antigen(s). © 1979 Springer-Verlag New York Inc.