Analysis of maternal IgG subpopulations which are transported into the chicken oocyte

Chicken serum and oocyte IgG were compared. Purified intact IgG and mercuripapain-produced Fc fragments of yolk and serum IgG were analysed by isoelectric focusing. All IgG bands were identical, indicating that all subpopulations of serum IgG were present in the yolk. Upon papain hydrolysis of both serum and yolk IgG, four identical Fc bands were produced from all serum and yolk samples. Sialic acid measurements showed that there was no significant difference in sialic acid content between serum and oocyte IgG. From these results we conclude that: (i) ovarian IgG receptor(s) selectively transports all subpopulations of maternal IgG; (ii) there is no selective destruction of IgG during transport; and (iii) yolk IgG has the same amount of sialic acid as the serum IgG.