Immunoglobulin allotype in the rat: localization of the specificity to the light chain.

An immunoglobulin allotypic antigen has been described in the rat. This antigenic specificity, called RI-1, is present on the IgG and IgM of the DA strain and is recognized by antisera raised in the Lewis strain. The anti-DA rat allotypic antisera were capable of precipitating I-labelled DA rat IgG and of agglutinating sheep erythrocytes coated with sub-agglutinating amounts of DA rat anti-sheep erythrocyte antibody. Inhibition studies with sub-units of DA rat IgG in the microprecipitin assay showed the RI-1 specificity to be on light chains but not on heavy chains of IgG.