Antigenic differences between spleen‐seeking and lymph node‐seeking thymus cells

Thymus cells of mice of the C3H and A strains were labeled with ⁴¹Cr and exposed in vitro to either normal mouse serum or to various antisera and the cells injected intravenously into syngeneic recipients. Exposure of thymus cells to various sera was found to have different effects on the cell subpopulations migrating to either the lymph nodes or the spleen. Anti‐H‐2 serum had a marked inhibitory effect on the migration of thymus cells to lymph nodes, and a much weaker effect on their migration to the spleen. Anti‐TH serum had a slightly stronger inhibitory effect on spleen‐seeking, as compared to lymph node‐seeking thymus cells. Anti‐Ly serum had a strong inhibitory effect on both migration streams. Anti‐TL serum had a stronger inhibitory effect on spleen‐seeking thymus cells than on lymph node‐seeking cells, a difference which became even more pronounced in cells exposed to Anti‐TL serum and complement. Normal guinea pig serum had a marked inhibitory effect on thymus cells migrating to the spleen, but hardly affected the lymph node‐seeking thymus cells. These results indicate that the thymus contains two major subpopulations of cells of differing antigenicity, which migrate to either the spleen or the lymph nodes. It is suggested that the different properties of T cells found in the spleen and in the lymph nodes result from the migration of different subpopulations of thymus cells to these organs.