Immunoglobulin a Production by Human Colostral Cells: Quantitative Aspects

Abstract

Similar to peripheral blood, human colostrum contains soluble host defense factors and immunologically active leukocytes. While these cells have been characterized with respect to morphology (1), surface markers (2) and some functional aspects (3,4), little is known about their role in the protection of the mammary gland or the recipient infant. Colostral leukocytes consist largely of macrophages and lymphocytes, both thymic dependent (T) and independent (B). However, unlike B lymphocytes from blood, those found in colostrum appear to be programmed toward production of antibodies of the IgA class (4) with specificity for antigens frequently encountered at mucosal surfaces (5). Further indication of the specificity of the antibody from colostral cells was derived from our study of oral immunization of pregnant women with a non-pathogenic strain of Escherichia coli (6). Utilizing a hemolysis-in-gel technique, we demonstrated the rapid appearance in human milk of cells secreting IgA antibody against the 0 antigen of the immunogen. Two further findings of this study provoked the present investigation. First, the appearance of antibody within the colostral leukocytes was not consistently accompanied by a rise in the level of secretory IgA (s-IgA) antibodies in colostral whey (5,6).