The ontogeny of B lymphocytes V. Lipopolysaccharide‐induced changes of IgD expression on murine B lymphocytes

Abstract

Murine splenocytes contain two minor subpopulations of B cells, one inducible by lipopolysaccharide to convert within 2 h from IgD⁻ to IgD⁺ and the other to change from IgD⁺ to IgD⁻. These two subpopulations can be separated by density centrifugation. Their relative proportions show a marked age dependency: IgD⁻ → IgD⁺ cells are more frequent in suckling mice, while IgD⁺ → IgD⁻ inducible cells become predominant in mice older than 3 weeks. The age dependency observed in the relative proportions between the two cell types suggests that they are ontogenetically related as progenitor-successor. This hypothesis is corroborated by phenotype analysis of the two subsets, revealing IgD⁻ → IgD⁺ cells as IgM⁺, Ia⁺, complement receptor⁻(CR⁻) and IgD⁺ → IgD⁻ cells as IgM⁺, Ia⁺, CR⁺. Our data show that IgD and CR are expressed concomitantly during B cell differentiation. On further differentiation, induced by lipopolysaccharide, both markers are lost from the cell surface at different rates: IgD decreases significantly in a very short period (8 h). The loss of IgD may thus herald an early differentiation event toward antibody-producing cells.