HUMAN BREAST-MILK LYMPHOCYTES-T DISPLAY THE PHENOTYPE AND FUNCTIONAL-CHARACTERISTICS OF MEMORY T-CELLS

Naive (unsensitized) and memory (antigen‐primed) T cells can be phenotypically distinguished on the basis of the high or low intensity with which they express a number of immunologically relevant lymphocyte membrane antigens, including CD45R, CDw29, UCHL1, LFA‐1, LFA‐3, CD2 and Pgp‐1. Here we report that in contrast to the two major T cell subsets found in the blood, milk T lymphocytes are almost exclusively composed of the one which exhibits the CD45Rlow, CDw29, UCHL1, LFA‐1high memory T cell phenotype. In addition, while milk and autologous blood cells expressed similar levels of CD3 surface antigens, CD2 and ICAM‐1 expression was approximately twofold greater on the milk T lymphocytes. This agrees with the finding that whereas colostrum T cells respond poorly to PHA, they proliferate and produce interferon‐γ normally when stimulated with either the anti‐CD3 or anti‐CD2 monoclonal antibodies. The selective colonization of the mammary gland during lactation by a population of T lymphocytes which displays the phenotype and functional characteristics of memory T cells may be one of the mechanisms whereby the suckling infant benefits from its mother's immunological experience. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim