Serologic identification of the human secondary B cell antigens. Correlations between function, genetics, and structure.

Abstract

The secondary B cell (SB) antigens are polymorphic HLA-linked antigens on human B cells and macrophages that are identified by primed T cell responses but are genetically distinct from the HLA-DR, MB and MT antigens. Serologic identification of the SB molecule, using the [mouse] monoclonal antibody ILR1, now makes it possible to correlate the function of these determinants in human T cell recognition with an Ia-like molecular structure and a genetic locus that marks a new HLA subregion. The following 3 lines of evidence indicate that the ILR1 molecule identifies an epitope on some alleles of the SB gene: the polymorphism of ILR1-reactivity in the population correlates with SB2, SB3; T cell proliferative response to SB2 and SB3 are specifically inhibited by ILR1; ILR1 reactivity is exactly concordant with the expression of SB2 in a panel of HLA-deletion mutant lymphoblastoid cell lines. The SB antigens are apparently on Ia-like molecules. The serologic studies of HLA-deletion mutant cell lines demonstrate that there are 2 HLA regions centromeric to HLA-B controlling expression of Ia-like molecules as follows: a region toward HLA-B that controls expression of HLA-DR, and a region toward GLO that controls expression of SB.