Colostral Leukocytes Research Articles

Separation of human colostral macrophages and neutrophils on gelatin and collagen-serum substrata.

A new technique for separation of human colostral macrophages and neutrophils was developed. Macrophages attached more readily to acid soluble collagen-serum or gelatin-serum substrata than neutrophils. Most of the adherent neutrophils were removed during the first 5 minutes incubation in 3 mM EDTA, thereafter, complete detachment of macrophages followed. Neutrophils and macrophages were enriched more than 80% in nonadherent cell populations and detached cell populations, respectively. These separated colostral leukocytes retained their viability and phagocytic activities. Therefore, functional studies of these purified human colostral leukocytes are possible.

Relationship between phagocytosis and immunoglobulin A release from human colostral macrophages.

Macrophages and neutrophils that contain mainly secretory immunoglobulin A (IgA) comprise the majority of cells in human colostrum. These cell populations were separated and analyzed for their ability to release total IgA and secretory IgA when stimulated to phagocytose. Colostral macrophages phagocytosed opsonized bacteria and nonopsonized latex particles; at the same time, IgA was released. Neutrophils poorly phagocytosed opsonized bacteria but actively phagocytosed latex particles. In contrast to the macrophages, the neutrophils did not release IgA, even after active phagocytosis of latex. Consequently, colostral macrophages are the main source of IgA released from colostral leukocytes when these cells are exposed to organisms or particles that are phagocytosed. A function for colostral neutrophils which sequester IgA is proposed.

Enhanced immunoglobulin, A release from human colostral cells during phagocytosis.

Human colostral leukocytes were investigated for their ability to release immunoglobulin A during phagocytosis of latex particles, heat-killed Candida albicans, or live Escherichia coli. Leukocytes readily phagocytosed latex or serum-opsonized candida or the E. coli. Colostral fluid was also opsonic for yeast and bacteria. Immunoglobulin release, which consisted mainly of secretory immunoglobulin A, began during the first 15 min of incubation with latex, opsonized yeast, or opsonized bacteria. Release was significantly increased from control levels by 30 or 60 min. The release of immunoglobulin A could be inhibited by incubating leukocytes at 4 degrees C. We conclude that phagocytosis and immunoglobulin A release by human colostral leukocytes are related. The data support the hypothesis that colostral leukocytes may play an active role in protecting infants from pathogenic microorganisms.

974 COLOSTRAL CELLS: IgA RELKASE STIMULATED DURING PHAGOCYTOSIS

Human milk leukocytes contain large quantities of IgA and other proteins. During prolonged in vitro incubation, the IgA is released. To further examine the potential role of this process in delivering these proteins to the recepient infant, the effect of phagocytosis upon the release of IgA from colostral leukocytes was investigated. Washed leukocytes were incubated with live Escherichia coli or heat-killed Candida albicans in the presence or absence of serum opsonins. The degree of phagocytosis was determined microscopically. Controls were incubated without particles. After 15, 30, and 60 minutes, cells and supernatant fluids were recovered and assayed for total IgA and SIgA by a quantitative immunofluorescence assay. The degree of IgA release was enhanced (approximately 40%) with cells exposed to opsonized organisms, as compared to preparations containing no particles. The degree of decrease in the IgA level in the cell lysates was paralleled by an increase in IgA in the supernatant fluids from the cell preparations. In contrast, little release occurred (approximately 4%) with unopsonized organisms. The enhanced release was evident within 15 minutes. Cells incubated with opsonized organisms at 4°C did not release IgA until warmed. The enhanced release of IgA by colostral leukocytes during phagocytosis may be part of a mechanism to deliver IgA antibodies to the site of microbial colonization or infection in the infant.

Immunoglobulin A production by human colostral cells: quantitative aspects.

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).KeywordsTotal CultureHuman ColostrumPlastic Microtiter PlateSecretory ImmunityLocal Lymphoid TissueThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Colostral leukocytes.

AbstractLeukocytes of human colostrum were studied for their phagocytic activity and ability to migrate in vitro. Samples were collected from healthy females in the first 2 weeks after delivery. Leukocytes were found with great regularity in concentrations of 2200–4100/mm3. These colostral leukocytes displayed glass adhesiveness, amoeboid movement, and the ability to migrate in capillary tubes. The phagocytic activity of colostral leukocytes against nonencapsulated Cryptococcus neoformans approached the normal values of peripheral blood leukocytes. The colostral leukocytes reacted to specific antigen similar to the donors' peripheral blood leukocytes and correlated with the dermal reactivity of the donor. The finding that these leukocytes are in relatively large numbers and possess phagocytic activity supports the concept that this is a naturally occurring in vivo phenomenon and that these cells may protect the breast against invading microorganisms; also, since these cells demonstrate the presence of cell‐mediated hypersensitivity and are normally ingested by the neonate, they may play a role in the development and/or induction of cellular immunity in the neonate.