IN VITRO STUDIES ON RADIATION LYMPHOID RECOVERY OF MOUSE SPLEEN

Abstract

Lymphoid regeneration following total body irradiation has been previously shown to be influenced by a humoral factor from the thymus. The present study was designed to test whether the thymus effects the lymphoid depleted spleen directly, or whether migration of cells from other tissue origins is also involved. Using the Millipore-filter-well technique for organ cultures, spleen fragments from irradiated adult mice were cultivated separately or in various combinations with thymus, bone marrow or lymph-nodes, in order to follow possible tissue interactions. It has been deomonstra-ted that a) Thymus from either untreated or irradiated donors did not stimulate spleen regeneration directly; b) Interaction between irradiated spleen and bone marrow from untreated donors led to the appearance of lymphoid cells, in contrast to cultures of the singly isolated tissues, where such cells were missing; and c) appearance of lymphoid cells was enhanced when thymus was added to spleen-bone marrow combinations. Experiments therefore indicate the thymus stimulatory effect on lymphoid regeneration may be mediated by bone marrow. The suggestions have been made, that in vivo, such inductive interactions take place by cell to cell contact, following cell migration, and that the lymphoid regeneration process operates by mechanisms similar as those involved in embryonic lymphoid development.