Immunoglobulins on the surface of lymphocytes in ontogeny

Immunoglobulins on the surface of lymphocytes from pig foetuses and newborn precolostral piglets were studied using iodinated monospecific anti-pig gamma- or mu-antisera. Labelling of cells was determined by autoradiography in light and electron microscope. Beginning with the 80th day of gestation the lymphocytes with surface IgM were detected in significant amounts in the spleen, whereas at earlier stages of prenatal development the IgM-bearing lymphocytes were detected rarely. The cells which carry surface immunoglobulins were classified as small lymphocytes with typical ultrastructural morphology.