Document Type

Dissertation - University Access Only

Award Date

2000

Degree Name

Doctor of Philosophy (PhD)

Department / School

Biology

Abstract

The relationship between the colostral environment and function of leukocytes in colostrum has been debated for the last 20 years. This study examines the ability of modified, acellular colostrum (MAC) to alter the phenotype of maternal peripheral blood mononuclear cells (PBM), and to affect their capacity to traffic into the circulation of neonatal calves. Further, in neonatal calves, we demonstrated the effects of colostral cells on several neonatal immune responses. Maternal PBM were exposed to culture media (supplemented RPMI 1640) containing 25% MAC or cultured for in medium alone for 24 hr. The expression of several homing and trafficking markers was assessed: (CDl la, CDl lb, CDI le, CD43, CD49d, CD49e, CD58, and CD62L). Modified, acellular colostrum treatment altered the percentage of cells expressing CD 11 a, CD l lc, CD43, and CD62L and the density of expression of CD 11 b, CD 11 c, and CD43 in comparison to freshly isolated mononuclear cells. ·The density of expression of CD62L and the percentage of cells expressing CD 11 a and CD43 were different for cells incubated in MAC from those cultured in medium alone. Maternal PBM, treated in the same way, with MAC or medium alone, were labeled with a fluorescent tracer (PKH26-GL) and fed to neonatal calves in colostrum within 6 hr of birth. Trafficking of these cells into the circulation of the neonate was monitored by flow cytometry. It was observed that: 1) only cells exposed to MAC appeared in significant numbers within the neonatal circulation, 2) the peak number of labeled maternal cells in the circulation of the neonate occurred between 12 and 24 hr after ingestion, 3) a large fraction of labeled maternal cells, composing ~3% of total circulating leukocytes at 24 hr after ingestion, were observed in the neonatal circulation. The capacity of PBM treated with either MAC or standard medium to bind to and migrate across intestinal epithelial tumor cells was examined using HT-29 and Intestine 407 cell lines. In addition, neonatal intestinal explant cultures were used to examine the migration of maternal leukocytes across ileal, jejunal, and colonic tissues in vitro. We demonstrated that migration takes place primarily across tissues derived from the jejunum and ileum of the neonatal small intestine. The explant cultures from the jejunum and ileum showed higher efficiencies of migration ( 11.6% and 22.8%, respectively) than those from colon (7.2%). Leukocytes treated with MAC or leukocytes treated with medium both had the same capacity to bind to and migrate across epithelial tumor cells in vitro. Cells from these treatments also demonstrated the same capacity to migrate across intestinal explant cultures. Therefore, the differences in the trafficking capacity of maternal leukocytes observed between PBM treated with MAC or medium into the neonatal peripheral blood appear to be attributable to differences in the capacity of the cells exposed to MAC to migrate into the circulation after crossing the neonatal intestinal tract, not in differences in their capacity to cross intestinal epithelium. CD 11 a was identified as a receptor that was partially responsible for the migration of leukocytes across neonatal epithelial cells. Blocking of CDl la on PBM with monoclonal antibody reduced the number of cells crossing neonatal explant cultures. In contrast, addition of monoclonal antibody against CD43 had no apparent effect on migration. The effects of colostral cells on neonatal immune responses were also evaluated in newborn calves. Neonatal calves were fed either cellular or cell-free maternal colostrum at birth and responses to maternal and unrelated MHC antigens were measured during the first 5 weeks of life using one-way mixed leukocyte responses (MLR). The overall proliferative capacity of neonatal cells was also evaluated using staphylococcus enterotoxin B (SEB), a superantigen stimulating T lymphocyte proliferation. Finally, the capacity of neonatal cells to function as stimulators in the MLR from both maternal and unrelated responder cells was measured. Maternal colostral leukocytes were shown to play an important role in the development of neonatal immune responses. Calves receiving cellular colostrum (CC) demonstrated enhanced responses to maternal and unrelated MHC antigens 24 hr after receiving colostrum. This corresponded with the period of peak trafficking of maternal colostral leukocytes into the neonatal peripheral blood in our earlier studies. Enhanced responses to SEB were also demonstrated 24 hr post-feeding in calves receiving CC, signifying an enhancement of the interactions required for cellular proliferation. Calves receiving cell free colostrum (CFC) showed no increase in responsiveness 24 hr post-feeding. The capacity of these calves to mount responses against MHC antigens developed at a much slower rate than calves receiving CC. These studies also indicated that antigen presenting cells appe.μ- to develop at a slower rate in calves deprived of colostral cells, as demonstrated by their poor ability to stimulate an MLR response with maternal and unrelated responder cells.

Library of Congress Subject Headings

Calves -- Immunology
Colostrum
Leucocytes
Maternally acquired immunity

Format

application/pdf

Number of Pages

114

Publisher

South Dakota State University

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