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

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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.