Figure 4.

Schematic models for the role of CD81 in Th2 responses. In the simplest model (A), CD81 on B cells interacts directly with a putative ligand on T cells, stimulating IL-4 production, which leads to IgG1 antibody production. The interacting T cells expressing CD81 ligand may be those already committed to Th2 development, or they may be recruited into this pathway upon interaction with B cells expressing CD81. In a slightly different model (B), B cells interact first with a subset of other B cells expressing the putative CD81 ligand. These B cells then interact with T cells via cell contact and/or soluble factors to induce IL-4 secretion and IgG1 antibody production.