BIOPHYSICAL AND IMMUNOLOGICAL STUDIES ON BOVINE IMMUNE GLOBULINS WITH EVIDENCE FOR SELECTIVE TRANSPORT WITHIN MAMMARY GLAND FROM MATERNAL PLASMA TO COLOSTRUM

Abstract

Three immune globulins in maternal serum and colostrum and newly born calf serum, have been characterized and compared. An examination was made to determine first, which of the maternal serum immune globulins accumulate in the circulation of the calf and secondly, the selectivity of the mammary gland for these proteins compared with the intestinal mucosa of the newly born calf. By difference in their electrophoretic mobilities three antigenically related immune globulins were isolated from bovine serum. The immune lactoglobulins in bovine colostrum were qualitatively similar to those in serum. However, marked differences were observed between the relative concentrations in serum and colostrum of the three immune globulins. An electrophoretically fast immune globulin (Cl), present in colostrum at high concentration, was shown to be antigenically similar to an immune globulin (Sl) present in the maternal serum at low concentration. These findings indicate that the mammary gland showed a highly selective preference for, and hence ability to concentrate in, colostrum, the electrophoretically fastest serum immune globulin. The slowest serum immune globulin and the component with intermediate electrophoretic mobility (S3 and S2 respectively) were both present at high concentration in bovine maternal serum, but were transmitted at different rates into the colostrum, so that the slowest immune globulin (S3) was present in the colostrum as a comparatively minor component (C3). In contrast to the mammary gland, the intestine of the newly born calf (permeable to undegraded protein during the first 24 hours of life) showed no selectivity. Immune globulins showing the three electrophoretic mobilities were absorbed equally readily. Thus, while the bovine mammary gland showed a highly selective perference for certain electrophoretically different serum proteins, no comparable selectivity was shown by the intestinal mucosa of the newly born calf. The results emphasize the heterogeneity of bovine immune globulins and show that the calf receives into its circulation from ingested colostrum selected maternal serum immune globulins. This selection of proteins from maternal plasma, for admission to the calf''s circulation, occurs within the mammary gland during the formation of colostrum but not during absorption across the calf''s intestinal mucosa.