LIGANDS AND BIOLOGICAL-ACTIVITIES OF SOLUBLE FC-GAMMA RECEPTORS

Soluble forms; of low-affinity Fc gamma receptors (sFc gamma R) circul ate in biologic fluids. Their plasmatic levels vary in immunological d isorders or related diseases. They are produced by enzymatic cleavage of the membrane receptors or by alternative splicing. They bind IgG wi th the same isotype specificity as their cell surface counterparts and thus modulate Fc-dependent immune functions. Recent data suggest that they also bind non-Ig ligands present on leukocytes. Functional impli cations of these findings are discussed.