The recruitment of recirculating lymphocytes in the antigenically stimulated spleen. Specific and non-specific consequences of initiating a secondary antibody response.

Antigenic stimulation of the rat spleen to initiate a secondary response to tetanus toxoid (tet. tox.) has been found to have two effects on the recirculating lymphocytes which are migrating through the splenic pulp. Firstly, specific antigen-sensitive cells were selected from a population of immune lymphocytes during migration through an isolated, perfused spleen which was stimulated with tet. tox. This was supported by the substantial, and mostly specific, depression in the ability of such migrated cells to mediate a secondary response to tet. tox. and by the large secondary response produced by transplanted fragments of the perfused spleen without further exposure to antigen. Secondly the i.v. injection of tet. tox. into rats which had been previously transfused with labelled immune lymphocytes or alternatively labelled non-immune lymphocytes was followed by a transient retention of both populations in the spleen at the expense of the lymph nodes. Any surplus retention of the immune population in the stimulated spleen was not detected which suggests with certain reservations that only a small minority of even the immune population were antigen-sensitive cells.