Effect of neuraminidase treatment on the expression of Fc IgG receptors on chicken embryonic bursa and thymus cells.

Bursa and thymus cells from chicken embryos at different ages were analyzed for Fc IgG receptors by EA-rosette technique and by binding of heat aggregated chicken IgG (agg IgG) in the indirect immunofluorescence test. Neuraminidase treatment resulted in a substantial increase of agg IgG binding cells both in the embryonic bursa and thymus. The binding of agg IgG was shown to be specific for Fc IgG receptors, since IgM and F(ab')2 fragments were not bound to neuraminidase-treated embryonic cells. A far lower percentage of EA-rosette-forming cells than agg IgG binding cells were found both in untreated and neuraminidase-treated bursa and thymus cells. It was concluded that neuraminidase can reveal additional Fc IgG receptor sites mainly for agg IgG on embryonic thymus and bursa cells.