Antigen-specific chemotaxis of B cells

The chemoattractant effect of soluble protein antigens for B cells from immunized mice was examined. Mice were immunized either via the footpad with ovalbumin (OVA) in complete Freund's adjuvant (CFA) or with CFA alone; or intraperitoneally with OVA incorporated in immune-stimulating complexes (OVA-ISCOM) or with saline. After 8-14 days B cells were purified from the spleens or the draining popliteal nodes and tested in vitro for locomotor responses to antigen using polarization (shape-change) and filter assays. Cells obtained by both routes of immunization, but not cells from control mice, gave locomotor responses to OVA. Responses were seen in B cells directly after preparation (5-8% of cells responding) but were enhanced if the cells were cultured overnight in the presence of interleukin-4 (IL-4) before testing (10-12% of cells responding). Checkerboard filter assays suggested that the response to OVA was chemotactic. The response was antigen specific since cells from OVA-immunized mice did not respond to bovine serum albumin (BSA), and cells from BSA-immunized mice responded to BSA but not to OVA. The response to OVA was inhibited by preincubation of OVA with anti-OVA but not with anti-BSA. Many of the cells that polarized in response to antigen were larger than any B cells found in control populations suggesting that the responsive cells are those that had been stimulated to enter cell cycle following immunization.