The major histocompatibility complex of outbred chickens. I. Analysis of the B13 haplotype by serology and cellular reactions.

The F antigens, which are serologically defined Class I gene products of the major histocompatibility complex in chickens (the B complex), were analysed in outbred birds. Private specificities of the F13 antigen from the inbred CC strain were detected in 20 outbred chickens by a haemagglutination technique. In the GVH-inhibition-release test F13 antigens from outbred and inbred chickens were identical. The L antigens, which are the Class II antigens of the B complex, were detected with specific anti L13 alloantisera by indirect immunofluorescence. Antisera defining the L13 antigen(s) of the inbred CC line reacted with all F13 positive outbreds. As a test of one-way direct compatibility of the inbred and outbred animals typing F13, graft versus host reactions were performed, injecting blood of F13 positive outbreds into inbred B13/13 eggs. No GVH stimulation attributable to MHC determinants was found. In MLR, responder cells from outbred MHC heterozygous chickens, which typed F13/x, were stimulated by inbred F13/13 homozygous typing cells, and weak, but significant, reactions were found. Further analysis in the accompanying paper, however, revealed no difference in the lymphocyte activating determinants (Lads) of inbred and outbred birds typing F13 and L13. No individual has yet been found which carries one of these antigens in the absence of the other.