Serological cross-reactivity of murine A.TH anti-A.TL antibody (anti-l-Ek antibody) with La-like molecules of human antigen-presenting cells.

The purified protein derivative (PPD)-specific proliferative responses of T cells from human peripheral blood are shown to be dependent on antigen-presenting cells (APC) which bear HLA-DR antigen detected by the monoclonal anti-HLA-DR antibody. The serological cross-reactivity of murine A.TH anti-A.TL antibody was observed in human APC. By absorption experiments using H-2 congenic mice, the serological cross-reactivity of A.TH anti-A.TL antibody with human APC is mapped in the I-E subregion. Thus, anti-I-Ek antibody reacts with the Ia-like molecule(s) on human APC. Murine allo-anti-I-Ek antibody does not always react with determinants of Ia-like molecule(s) on human APC, since this antibody did not eliminate PPD-specific proliferative responses in one particular case. Thus, anti-I-Ek antibody seems to react some type of the polymorphic determinants but not of the shared determinants of human Ia-like molecule(s) on APC. The relationship between the cross-reactive molecule detected by murine allo-anti-I-Ek antibody and the HLA-DR antigen remains to be analyzed.