IL-4-induced B cell migration involves transient interactions between beta 1 integrins and extracellular matrix components.

IL-4 has previously been shown to stimulate motile responses in murine B lymphocytes. This was studied as acquisition of motile morphology and migration through filters in microchemotaxis chambers. In this paper, we investigated IL-4-stimulated migration of B cells into gels of native collagen fibers, which may be a more physiologically relevant assay. When IL-4 was present in the gel and/or in the medium above, B cells were able to invade the collagen gel. Migration was dependent on the dose of IL-4 and was optimal after 45 h of incubation. It appeared that IL-4 acted by inducing both chemokinesis and chemotaxis. Fibronectin (FN) was found to be an important factor for B cell locomotion, since low concentrations of FCS or FN in the gel matrix greatly improved migration. B cell locomotion was inhibited by antibodies specific for beta 1, alpha 4 and alpha 5 integrins, indicating the presence of integrin-extracellular matrix (ECM) interactions in lymphocyte motility responses. Migration was not associated with an up-regulation of beta 1, alpha 4 or alpha 5 integrins. The adhesion between substrate and cells is likely to be of low affinity, since IL-4-stimulated, as well as non-stimulated B cells, did not adhere to ECM-coated culture wells. Our data suggest that transient interactions between integrins and the ECM matrix may favour B cell migration.

CD23 and CD21 function as adhesion molecules in homotypic aggregation of human B lymphocytes.

We have previously found that interleukin-4 and CD40 monoclonal antibodies (mAb) are strong potentiators of homotypic B cell aggregation which is dependent on LFA-1. We show here that CD23 mAb were also able to inhibit aggregation to a similar extent as LFA-1 antibodies. This inhibition was restricted to the MHM6 epitope of CD23 and antibodies to other epitopes [Epstein-Barr virus (EBV) CS-1, EBV CS-2, EBV CS-5 and mAb 25] or occupation of the Fc-binding site by IgE had no or a slightly enhancing effect on aggregation. When testing two antibodies to CD21, the recently defined ligand for CD23, one of these (BU32) was found to be inhibitory whereas the other (THB5) had no effect. By combining antibodies to LFA-1 and CD23, aggregation was often completely inhibited. These data suggest that LFA-1/ICAM-1 and CD23/CD21 are the major molecules involved in homotypic aggregation of human B cells.

CD2: a functional adhesion molecule on murine B cells, involved in interleukin-4-induced aggregation.

The murine equivalent to CD2, previously known as a T cell marker, is expressed on mouse B cells. The monoclonal anti-CD2 antibody 12-15 was found to induce B cell homotypic adhesion. When treated with F(ab')2 fragments of 12-15, purified, resting B cells aggregate within 2 h of incubation and the response is optimal after 20 h. Anti-CD2-induced aggregation is a dose-related active process, dependent on temperature, metabolic energy and divalent cations. Aggregation is inhibited by two different Fab monomers of anti-CD2, implying that it is the CD2 molecule itself that functions as an adhesion molecule. We also report that interleukin 4-induced B cell homotypic adhesion involves CD2-mediated cell binding, since the antibodies specific for mouse, CD2, inhibited interleukin-4-induced cell aggregation.