Inhibition of adoptive secondary responses by lymphoid cell populations

The ability of normal and tolerant lymphoid cells to inhibit the adoptive secondary response was investigated in order to delineate the influence which the host can exert on a memory cell population as the host recovers from the effects of irradiation. LBN rats were irradiated with 500R whole body X-irradiation, reconstituted with either normal or tolerant lymphoid cells, then they were given immune spleen cells and challenged with soluble antigen (DNP-BGG). Cells capable of suppressing the adoptive secondary responses were shown to possess the following characteristics: 1) in nonimmune donors they were found in the greatest concentration in lymph nodes, followed by spleen and bone marrow and were practically absent in the thymus; 2) their numbers were not increased in donors rendered tolerant by long term treatment with deaggregated DNP-BGG plus cyclophosphamide nor in donors given large doses of DNP-BGG 48 to 72 hr before sacrifice; 3) in animals rendered tolerant by long term antigen treatment alone some enhancement of suppressor function was seen; 4) the suppressor cells could be shown among both glass wool adherent and nonadherent cells and 5) the nonantigen specific suppressor cells did not affect the kinetics of antibody formation nor the affinity of the antibody which was produced. These results are discussed in terms of the nature and source of the suppressor cell populations and their relevance to the control of secondary responses in intact animals.