Peanut agglutinin. VI. Identification of murine T lymphocyte subsets during ontogenesis by use of peanut agglutinin and Ly-6.2 antiserum.

Fluoresceinated peanut agglutinin (PNA-FTC), Thy-1.2, and Ly-6.2 antisera were used to identify various murine T lymphocyte subpopulations during fetal and perinatal life. By means of double immunofluorescence labeling, we identified three T lymphocyte subsets: PNA+Ly-6.2+, PNA+Ly-6.2-, PNA-Ly-6.2+ having distinct distribution in the adult thymus and spleen. The study of the appearance of these three subsets in fetal liver, thymus, and spleen has shown that they did not occur similarly. The PNA+Ly-6.2+ subset was present in all three organs during fetal life and at a level rather similar to that of adult life; the PNA+Ly-6.2- subset was also present in the three fetal organs; conversely, the percentage of the PNA-Ly-6.2+ spleen cells was very low in fetal and neonatal life and increased significantly between 1 and 2 wk of age. Our results demonstrate that during fetal life, lymphocyte subsets are phenotypically differentiated as in adult life and that differentiation of T lymphocytes occurs preferentially through various lineages present during early ontogenesis. Moreover, quantitative modulation of some of these subsets is shown from fetal to adult life and may explain some of the immunologic immature features of young murine spleen.