Signalling processes induced by ligation of B-cell receptor (BCR), complement receptor type 2 (CR2) and FcγRII with opsonized antigen and immune complexes. Ag, antigen; IC, immune complexes; IgG, immunoglobulin G; IgM, immunoglobulin M; ITAM, immunoreceptor tyrosine-based activation motif; ITIM, immunoreceptor tyrosine-based inhibition motif; Ops. opsonized; PI-3K, phosphatidylinositol-3 kinase; PTK, protein tyrosine kinase; SHIP, inositol phosphate 5-phosphatase; SHP-2, protein tyrosine phosphatase, SHP-2; Vav, guanidine nucleotide exchange factor, Vav. ↑, activation; ↓, inhibition; –, no effect; *, for Ag-specific or non-specific B cells, respectively.