PEANUT AGGLUTININ .3. STUDY OF LYMPHOCYTE-T DIFFERENTIATION DURING MURINE ONTOGENY

Peanut agglutinin (PNA) is a nonmitogenic lectin useful for studying lymphocyte differentiation in mouse lymphoid organs during gestation and after birth. PNA-positive (PNA+) cells are found early during gestation: on the 14th day in the thymus, on the 18th day in the spleen. Some PNA+ cells are found in the fetal liver before the thymic rudiment is fully colonized. In the 14-day thymus, both PNA+ and PNA- cells are present but the proportion of PNA- cells is higher than that of PNA+ cells. Regarding thymus development with age, we have separated thymocytes on discontinuous Ficoll gradients; in the dense layers, both PNA+ and PNA- thymocytes increase during thymus development and then decrease only slightly during thymus involution. Conversely, in the light layers, both PNA+ and PNA- subpopulations decrease significantly from 18 days of age; by three months of age these populations are smaller than for neonates. © 1979 Pergamon Press Ltd. All rights reserved.