Early Growth Response-1 Plays a Non-redundant Role in the Differentiation of B Cells into Plasma Cells

Early growth response (Egr)-1 is a Cys(2)-His(2)-type zinc-finger transcription factor. It has been shown to induce survival and proliferation of immature and mature B cells, respectively, but its role in the differentiation of B cells into plasma cells remains unclear. To examine the effects of Egr-1 deficiency on the activation of B cells, naive B cells from Egr1(-/-)mice and their wild-type (WT) littermates were activated to proliferate and differentiate, and then assayed by FACS. Proportions of cells undergoing proliferation and apoptosis did not differ between Egr1(-/-)and WT mice. However, Egr1(-/-)B cells gave rise to fewer plasma cells than WT B cells. Consistently, Egr1(-/-)mice produced significantly lower titer of antigen-specific IgG than their WT littermates upon immunization. Our results demonstrate that Egr-1 participates in the differentiation program of B cells into plasma cells, while it is dispensable for the proliferation and survival of mature B cells.