The appearance of an IgD-like molecule on pig lymphocytes during ontogeny

An IgD-like molecule was found on the surface of pig fetal lymphocytes using guinea pig anti-human IgD antisera and indirect immunofluorescence. The binding of antiIgD antisera could be specifically inhibited with human IgD. Surface IgD-like molecules were found later in ontogeny than surface IgM (after about 70 d of gestation in the spleen). There is evidence for their endogenous origin. The number of lymphocytes bearing IgD-like molecules rapidly increased during ontogeny.