A newly defined murine alloantigen controlled by the S region of the H-2 complex: molecular association with the...

A previous study has shown that prolonged immunization of strain A.TBR16 mice (H-2 haplotype at16) with lymphoid tissue derived from A.TBR13 (at13) donors results in an antiserum that defines a new H-2-associated allotype with a strain distribution antithetical to H-2.7. The present report describes a sensitive ELISA that demonstrated that this specificity represents an allotypic determinant(s) on the fourth component of complement (C4). Studies with Sephadex G-200 fractionated plasma and serum proteins suggest that, as is the case for H-2.7, the new specificity appears to reside on the C4d fragment after C activation. We therefore propose the tentative nomenclature C4d.2 for this specificity and suggest revision of the nomenclature for H-2.7 to C4d.1. Also described in this report is the formal mapping of the genetic control of the C4d.2 allotype to the H-2S region.