The effect of fluorescein conjugation on Fc-dependent properties of rabbit antibody.

Conjugation of rabbit antibody with fluorescein isothiocyanate results in loss of the ability of that antibody to fix complement, mediate passive cutaneous anaphylaxis, or participate in cytophilic binding to macrophage surfaces. Fluorescein, perhaps because of molecular size or configuration, is a more potent suppressor of Fc function than are other reagents previously studied in this regard.