Am J Reprod Immunol. 1997 May;37(5):378-83. Unique Identifier : AIDSLINE
PROBLEM: Determination of lactation stage-dependent changes in levels of
lymphocyte subpopulations in milk. METHOD: Flow cytometric assay was
used to identify and assay lymphocyte subpopulations in bovine milk at
different stages of lactation. RESULTS: Lymphocyte subpopulations in
mammary secretions of dairy cows change during the lactation cycle. In
involuting glands (dry gland), approximately 80-90% of lymphocytes were
CD2+ T cells. The proportion of CD2+ T cells, however, decreased to
approximately 50% at the colostral stage an fluctuated between 50 to 60%
in normal (mature) milk. Throughout the lactation stages, less than 5%
were B cells as identified by the monoclonal antibodies against CD21 and
MHC class II antigens. Subset analysis showed, however, that the
proportion of CD5+ T cells decreased from 90% in involuting gland
secretions to 75% in colostrum (peripartum stage), and to approximately
40-50% in the normal (mature) milk, CD4+ T cells constituted between 45
to 55% of lymphocytes in the dry gland secretion but decreased
drastically at parturition and maintained at the level below 20%
throughout normal lactation. In contrast, the proportion of CD8+ T cells
in the dry gland secretion was low, between 30 to 40%, but increased
steadily, in an inversely-related manner with that of CD4+ T cells, to
approximately 40-50% at parturition and maintained at approximately
30-40% during the normal lactation stage thereafter. Two-color
immunofluorescence study revealed further that practically all of the
CD8+ cells in dry gland secretions were CD2+, and approximately 40% of
them were CD5-. Throughout the lactation cycle, WC1+ gamma delta T cells
comprised only 2 to 5% of lymphocytes in mammary secretions.
CONCLUSIONS: T lymphocyte subpopulations change dynamically during
stages of the lactation cycle. The selective migration of T lymphocyte
subpopulations to and from the mammary gland, and their functional roles
in the immune competence and regulation of the dam and sucklings remain
to be elucidated.
*CD4-CD8 Ratio *Lactation/IMMUNOLOGY *Lymphocyte Subsets/IMMUNOLOGY
*Milk/IMMUNOLOGY