Cell mediated lympholysis in man. The HL-A third locus antigen, AJ (W20) as sensitizing and/or target determinant

The Indirect Cell Mediated Lympholysis (ICML) test has become a reliable in vitro tool in investigations of the immunogenetic background of the cellular immune response. It is well established that the antigens of the LA and FOUR loci of the human Major Histocompatibility Complex (MHC) or antigens governed by closely linked loci exhibiting a marked linkage disequilibrium are of major qualitative and quantitative importance in ICML. This communication is concerned with the importance of the HL-A third series antigen AJ (W20) on lympholysis in ICML. From investigations of 47 combinations where only the AJ (W20) antigen may be attacked, it is concluded that this antigen is, in itself, a poor ICML target determinant, but that AJ (W20) may function as a stronger ICML target determinant in concert with a FOUR antigen, although the actual FOUR antigen cannot be attacked.