T--Lymphocyte Recognition of the I--EC Gene Products (la) Requires Concomitant Recognition of I--AB Gene Products.

The murine primed lymphocyte typing (mPLT) assay, based on the sequential reactivation of specific immunocompetent, alloantigen-reactive T blast cells in secondary mixed leucocyte culture (MLC), has been utilized to define the class II I-EC-subregion-associated lymphocyte-stimulating (LS) determinants of the major histocompatibility complex (MHC). The test panel of secondary stimulating cells has been expanded in this study to include the B10.W lines (mouse strains carrying MHC regions derived from wild mice). Data obtained using mPLT cells generated in primary MLC between I-EC-subregion-disparatestrain combinations reveal that(1) an absolute correlation between expression of the serologically defined Ia specificities and the capacity to induce subsequent secondary MLC activation does not exist, and (2) whereas the serologically defined Ia specificities appear to cluster on the α-chain of the Ia molecule, T lymphocytes recognize either the β-chain per se or an interaction product of the α-chain plus β-chains. Based on these observations, we conclude that T and B lymphocytes recognize different antigenic moieties expressed on the MHC class II antigens. How these data explain and/or affect several genetic concepts is discussed. [ABSTRACT FROM AUTHOR]