The expression of immunoglobulin determinants on the surface of antigen‐binding lymphoid cells in mice. II. Allotypes of the lg‐1 locus

Inhibition of rosette‐forming cells by anti‐immunoglobulin sera has been used as a model system to investigate the phenotypic expression of IgG 2a allotypes on the surface of mouse spleen cells reactive against sheep erythrocyte antigens. The evidence presented suggests that reactive cells from mice heterozygous at the Ig‐1 locus may not be restricted to the expression of the product of only one parental allele on their surface. Control studies with mixtures of cells from mice compatible with respect to H‐2 antigens but differing at the Ig‐1 locus suggest that this finding is not the result of a passive absorption phenomenon. This apparent lack of allellic exclusion was demonstrated with cells harvested during the early part of the response to a primary injection of antigen. Reactive cells later in the immune response appeared to be restricted to the expression of one parental allotype.