[Regulation of immunoglobulin production: role of the cellular receptors for the Fc portion of these molecules].

The aim of this paper was to review the action of the receptors for the Fc portion of Ig on the polyclonal activation of human B lymphocytes. The IgG Fc fragments were shown to be digested by monocytes into peptides which triggered B-cell differentiation and the release of a T-cell replacing factor termed (Fc)TRF. In the presence of PWM and monocytes, unbound aggregated IgG suppressed B-cell differentiation into Ig-synthesizing cells. This suppression was not isotype-specific. After having bound aggregated IgG, T cells were able to display an isotype-restricted suppression of B-cell differentiation induced by PWM. Finally, soluble Fc gamma R released from T or B lymphocytes or neutrophils were found to inhibit both the synthesis of IgG and the maturation of B cells into IgM or Ig A-secreting cells.