Regulation of murine MHC class II molecule expression. Identification of A sub(beta) residues responsible for allele-specific cell surface expression

A panel of mutant class II genes have been constructed using site-directed mutagenesis and DNA-mediated gene transfer. Using this technique, A super(k) beta polypeptides have been altered by substituting one or more A super(d) beta-specific residues at polymorphic positions in the beta sub(1) domain. Transfection of M12.C3 B lymphoma cells with most mutant A super(k) beta * genes results in the expression of A super(k) beta * A super(d) alpha molecules on the cell surface. However, the substitution of a single d allele residue at position 78 or 86 in the A super(k) beta polypeptide results in either the complete absence or very low levels, respectively, of cell surface expression of the A super(k) beta * A super(d) alpha molecule, but does not alter A super(k) beta * A super(k) alpha expression.