The existence and distribution of T lymphocyte subpopulations in the mammary parenchymal tissue of cows were immunohistochemically detailed during early lactation. CD2+, CD4+, and CD8+ T lymphocytes were localized primarily in the mammary parenchymal tissue. CD8+ T lymphocytes were predominant over CD4+ T lymphocytes and occurred in close contact with the alveolar epithelium and between epithelial cells in the central area of the upper mammary gland. CD4+ T lymphocytes were present in equal numbers in the epithelial and connective tissue area. Occasionally, both CD4+ and CD8+ T lymphocytes formed cell clusters in the interalveolar connective tissue. The ratio of CD4+ T lymphocytes to CD8+ T lymphocytes was less than 1.0 and was lower in the epithelial area than in the connective tissue. The distribution of CD4+ and CD8+ T lymphocytes was similar in the parenchymal tissue of the gland cistern. The observation that there is a preferential presence of CD8+ T lymphocytes in the epithelial area of the bovine mammary gland during early lactation might indicate that these cells participate in the maintenance of the integrity of the epithelium.

No abstract

No abstract

No abstract

No abstract