Locomotor properties of human germinal centre B cells: activation by anti-CD40 and IL-4 allows chemoattraction by anti-immunoglobulin.

The locomotor properties of B cells isolated from the germinal centres (GC) of human tonsils were studied using polarization, collagen gel invasion and micropore filter assays. The proportion of motile GC cells in the freshly isolated population was small. During culture in interleukin-4 (IL-4)+anti-CD40, but not in control medium, the proportion of polarized cells increased and these cells migrated actively into collagen gels. After 24 hr culture, most of the surviving population was in locomotor morphology. The locomotor population consisted mainly of centrocytes in the G1 phase of growth. More locomotor cells than spherical cells took up [3H]uridine, but locomotor cells did not take up [3H]thymidine. After culture for 6 hr in IL-4+anti-CD40, GC B cells were tested in short-term polarization assays and filter assays for their response to chemoattractants. In both assays, a proportion of the cells responded to anti-IgA and to anti-IgA F(ab')2 fragments at 1 ng/ml., or to anti-IgG, anti-IgM and F(ab')2 fragments of these antibodies at 100 ng-1 microgram/ml. A checkerboard filter assay showed a good chemokinetic response and a weaker chemotactic response of GC cells to anti-IgA. Expression of Fc gamma RII (CD32) was increased after culture in IL-4+anti-CD40, and these cultured cells responded in filter and polarization assays to anti-CD32. Thus culture in IL-4 and anti-CD40 not only rescues GC B cells, but also increases their locomotor capacity and allows them to respond in chemotaxis assays to anti-immunoglobulin.