Suppressor cell influence in selected strains of inbred rats. III. Evidence for nonspecific suppression by a lymphocyte-macrophage cooperation.

Lewis (LE) and Brown-Norway (BN) rats treated in vivo with rabbit anti rat thymocyte serum demonstrate a reversal in relative responsiveness when assayed to mitogens and antigens via lymphocyte transformation, i.e., the BN rat now responds to a greater magnitude than the LE rats. Spleen cells, from both strains, that have been eluted from glass wool columns, demonstrate elevated responses to mitogens and antigens when compared to unfractionated spleen cells. The responses by these unfractionated and nonadherent populations can 1) be further enhanced subsequent to the treatment with anti-thymocyte serum and 2) suppressed after addition of macrophages from either strain, but especially by BN derived macrophages. The adherent cells from LE spleens respond to the above treatments in a similar fashion as the other populations. The responsiveness of adherent BN cells is only partially restored following treatment with anti-thymocyte serum, and is not further suppressed upon the addition of macrophages. These data are indicative of a lymphocyte-macrophage cooperation in this mechanism of suppression.