Herein we demonstrate that B cell-activating factor of the TNF family (BAFF), a B cell survival factor, also regulates CD21/35 and CD23 expression. BAFF blockade in wild-type mice down-modulates CD21/35 and CD23 on B cells while survival remains intact, and BAFF exposure causes elevated CD21/35 and CD23 expression. Similar down-modulation is observed in bcl-2-transgenic mice treated with a BAFF inhibitor. This is the first evidence that BAFF has a function independent of B cell survival. Reports using CD21/35 and CD23 expression to assess splenic B cell subsets in BAFF-null mice concluded a lack of B cells beyond the immature stage. Since CD21/35 and CD23 are inadequate for delineating B cell subpopulations in BAFF-null mice, we used expression of BAFF-R and several B cell markers to identify more mature splenic B cells in these mice. These data broaden our understanding of BAFF function and correct the view that BAFF-null mice lack mature B cells.

Monoclonal antibodies (MAbs) raised against wing tissues of Manduca sexta recognize epitopes shared by both hemocytes and basal laminae. During the last larval stadium, the basal lamina of moth wing epithelium forms after hemocytes have migrated into the space adjacent to basal surfaces of epithelial cells. As adult development commences, hemocytes participate in phagocytosis of the same basal lamina; and as dissolution of the basal lamina proceeds (day 2-day 5 post-pupation), wing epithelial cells send forth long basal processes and rearrange within the plane of the epithelium. During this period of cell rearrangement, the immunoreactivity of the basal lamina decreases in concert with an increase in immunoreactive vesicles within hemocytes; and at the ultrastructural level, hemocytes have been observed to engulf fragments of basal lamina. The distribution of immunolabel in the developing moth wing suggests that hemocytes contribute not only to the formation of the wing's basal lamina but also to its breakdown. Since basal laminae are probably important determinants of epithelial form and pattern, hemocytes also contribute to the shaping of epithelial populations.