Horse IgG- and ostrich IgY-F(ab′)2 groups have different affinities for mice erythrocytes and lymphocytes. Implications for avian immunoglobulin therapeutic usefulness

► We studied the interaction of IgY, F(ab′)2 and IgG with mice lymphocytes and erythrocytes plasma membrane. ► The Igs were labeled with fluorescein isotiocyanate (FITC) and observed with deconvolution fluorescence microscopy. ► IgY interact with lymphocyte plasma membrane without endocytosis of the labeled protein. ► Erythrocytes exposed to horse Igs became intensely fluorescent for at least 5 h, no labeling occurred with FITC-IgY. ► IgY may be a stronger activator of adaptive immunity than horse IgG in mammals.