Immunoregulation by Fc signals. A mechanism for self-nonself discrimination

B-cell activation is regulated by several means, among them the feedback effect of secreted antibody, which binds to antigen on antigen receptors and to the B cells' Fc receptors. In the view of N. R. Sinclair and A. Panoskaltsis, outlined here, this repressive influence is exerted early in an immune response but can be relieved by various T-cell factors. These include rheumatoid factors which, by binding specific antigen as well as blocking repressive Fc signals, may permit immune responses to proceed. Aberrant production of rheumatoid factor may deregulate suppressed self-reactive B cells, triggering autoimmune responses.