| Abstract: | Bovine-associated mucoprotein (BAMP), solubilized with water from the delipidated membranes of bovine milk fat globules, is not restricted to fat globules or to the alveolar epithelial cells from which they are formed. BAMP also has a widespread distribution on other bovine glandular epithelial cells and on undifferentiated cells in lymphoid germinal centers and in several fetal tissues. Free BAMP is present in bovine colostrum, milk, other secretory fluids, and in fetal serum but is absent from adult and colostrum-deprived calf sera. In bronchoalveolar fluids, BAMP is preferentially found in the mucus-rich fraction. BAMP is antigenically distinct from all adult serum proteins, free secretory component, beta 2-microglobulin, lactoferrin, alpha-lactalbumin, beta-lactoglobulin, and five different caseins. BAMP as a free protein constitutes one-sixth of the total amount of BAMP present in milk. The BAMP-related component of fetal serum lacks antigenic determinants present on the BAMP of milk as demonstrated by immunoprecipitation and partial blocking of immunofluorescence. The fetal component is not fetuin or alpha 1-fetoprotein. These data suggest that BAMP may be useful in studies of the membranes of proliferating or differentiating epithelial cells. |
