ALVEOLAR MACROPHAGES .6. REGULATION OF ALVEOLAR MACROPHAGE-MEDIATED SUPPRESSION OF LYMPHOCYTE-PROLIFERATION BY A PUTATIVE T-CELL

  • 1 January 1981
    • journal article
    • research article
    • Vol. 42  (1) , 137-147
Abstract
Alveolar macrophages (AM) from normal rats suppressed antigen- or mitogen-stimulated blastogenic responses in cultures of splenic or lymph node lymphocytes, high suppression levels often being observed when added AM comprised as few as 0.6% of the total cells in culture. The efficiency of AM-mediated spleen cell blastogenesis suppression declined with spleen cell donor age, was severely curtailed by donor pretreatment with low cyclophosphamide levels and was depleted by adult thymectomy coupled with thoracic duct drainage. AM suppressive activity was most obvious at high cell density, was unaffected by the presence of indomethacin in the cultures, or by prior spleen cell X-irradiation. Spleen cell fractionation by velocity sedimentation yielded cell populations of greatly varying sensitivities to AM-mediated suppression, from small splenocytes (sedimentation velocity 1.1-2.8 mm/h) which were almost totally refractory to AM-suppression when assayed in isolation from the remainder of the spleen cell population, to larger cells (sedimentation velocity > 3.5 mm/h) exhibiting high sensitivity levels. Spleen cell fractionation by glass wool adherence indicated decreased sensitivity to AM-suppression in the effluent population. Examination of the suppressive activity of individual AM subpopulations separated by velocity sedimentation indicated that the larger macrophages were the most active in vitro. Suppressive activity of this nature was not seen with unstimulated peritoneal macrophages, but was observed when activated peritoneal exudate cells were tested. A 2-cell model for blastogenesis suppresion is proposed, the ultimate effector cell being a macrophage, the activity of which is controlled by a long-lived, recirculating lymphocyte, which was provisionally designated as a T lymphocyte.