Cellular heterogeneity in the thymus. II. Distribution patterns of different lymphocyte populations in chickens.

Abstract

AbstractLymphocyte preparations from chicken blood, spleen, bursa, as well as fractionated thymus cell preparations, were labeled in vitro with 51Cr and reinjected into various groups of recipients. The relative distribution patterns of labeled cells in numerous recipient organs remained practically unchanged after different time intervals, but were significantly different for the various cell preparations.The distribution patterns provided additional evidence for the existence of different lymphocyte subpopulations in the thymus of young chickens, one of which is bursa‐dependent. Thymus cell preparations fractionated by differential centrifugation showed significant differences in their accumulation in the spleen and liver. The analogous lymphocyte preparations from neonatally bursectomized birds showed no such differences. Cells from 6‐month old donors gave results similar to those obtained with cells from young bursectomized birds, suggesting that the bursa‐dependent subpopulation in the thymus disappears after involution of the bursa.An unexpected finding was the rather large accumulation of blood lymphocytes in the thymus of the recipients. This observation stands in contrast to the concept of a blood‐thymus barrier.