The effect of T cell-derived cytokines on B cell motility in vitro.

We have investigated the ability of interleukin-1 (IL-1), IL-2, IL-3, IL-4, IL-5, IL-6, and interferon-gamma (IFN-gamma) to induce motility in murine, splenic B lymphocytes. Two parameters of cellular locomotion were studied, namely acquisition of motile morphology (polarization) and in vitro migration through polycarbonate filters. Of the tested cytokines, only IL-4 gave a strong motile response among B cells. At the optimal concentration of 3 ng/ml, IL-4 induced polarization in 10-20% of the B cells within 30 min and in up to 40% after overnight exposure. The same amount IL-4 present in a microchemotaxis chamber stimulated migration through polycarbonate filters after overnight incubation in up to 15% of the input B cells. IFN-gamma could also induce some degree of polarization and migration, but only after 19 hr of exposure and to a much lesser extent than IL-4.

T and B cell collaboration: induction of motility in small, resting B cells by interleukin 4.

In this report we investigate if IL 4 can work as a chemoattractant factor by inducing locomotion in B cells. We found that murine recombinant IL 4 (rIL 4) induced motile morphology and migration through polycarbonate micropore filters of murine, splenic B cells at an optimal concentration of 3 ng/ml. Kinetic studies revealed optimal migration at 8-16 h, although a significant response could be detected already after 1 h. Flow cytometric studies confirmed that the migrated cells were indeed B cells. We also compared the activity of small, dense B cells and large, low-density B cells, based on Percoll gradient separation. We found no difference in IL 4-induced motility among the two groups. Furthermore, we looked at B cells activated in vitro by preculture in lipopolysaccharide (LPS) or IL 4. Our data indicate that both LPS and IL 4 can increase the general capacity for motility in B cells after preculture for 24 h. T and B cell collaboration requires close cell-cell contacts in order for T cell help to be administered to the B cell. One way of enhancing such cell contacts could be through directional cell migration induced by helper factors (chemotaxis). We suggest that IL 4 can play a role as a chemoattractant factor that enhances cell contacts between T helper cells and B cells.

Interleukin 4 induces cellular adhesion among B lymphocytes.

We here report that interleukin 4 (IL-4) alone is able to induce cellular adhesion among mouse lymphocytes, and together with lipopolysaccharide (LPS), it increases the adhesion induced by LPS. The adhesion was inhibited by antibodies against IL-4. IL-4 appears to be acting mainly on B lymphocytes, since the response caused by IL-4 alone was much less sensitive to depletion of adherent cells than the LPS response. Depletion of T cells had no effect on IL-4- or LPS-induced adhesion. IL-4 could together with Con A, but not alone, induce adhesion among T cells. Cell clusters, which were formed after 2-3 days of LPS plus IL-4 stimulation, could be completely dissociated, and when the cells were recultured in medium, they readily started to reaggregate. The adhesion molecule lymphocyte function-associated antigen 1 (LFA-1) is, at least in part, involved in LPS plus IL-4-induced adhesion. Antibodies against LFA-1 inhibited the adhesion, but antibodies against other cell surface molecules were without inhibitory effect. Adhesion induced by IL-4 alone may involve other adhesion molecules than LFA-1.