Page 758 - Veterinary Immunology, 10th Edition

VetBooks.ir Cell-Mediated Immunity and

Colostrum

Colostrum is full of lymphocytes, but milk is not. Sow colostrum
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contains between 1 × 10 and 1 × 10 lymphocytes/mL. Of these, 70%
to 80% are T cells. Within 2 hours after receiving colostrum that
contained labeled cells, maternal lymphocytes appeared in the

bloodstream of piglets. Piglets that had received these colostral cells
showed enhanced responses to mitogens compared with control
mammals. Transcriptome analysis of colostral T cells in sows has
indicated that they are more activated than peripheral blood T cells.
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Bovine colostrum also contains between 3 × 10 and 1 × 10 5
lymphocytes/mL, about half of which are T cells. Colostral
lymphocytes may survive up to 36 hours in the intestine of
newborn calves, and some may penetrate the epithelium of Peyer's

patches and reach the lacteal ducts or the mesenteric lymph nodes.
Cell-containing and cell-free colostrum have been compared for
their ability to protect calves against enteropathic E. coli. The calves
receiving colostral cells excreted significantly fewer bacteria than

those receiving cell-free colostrum. The concentration of IgA- and
IgM-specific antibodies against E. coli in the serum of neonatal
calves was higher in those that received colostral cells than in those
that did not. The calves that received colostral cells had better

responses to the mitogen concanavalin A and to foreign antigens
such as sheep erythrocytes. The mechanisms of this protective effect
are unclear.
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The CD8 T cells in bovine colostrum can produce large
quantities of IFN-γ that may influence the early development of
Th1 responses in neonatal calves. Thus ingestion of maternal
colostral cells appears to accelerate the development of activated
calf lymphocytes. The monocytes of calves that received colostral

cells are more capable of processing and presenting antigens.
Transfer of cell-mediated immunity by bovine milk lymphocytes
has been demonstrated. Pregnant cows were vaccinated against
BVDV. Blood lymphocytes from calves that received cell-free

colostrum from these cows were unresponsive to BVDV antigen. In

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