Macrophages as Regulatory Cells in Mitogen Induced Spleen Cell Proliferation. 1. Macrophages as Suppressor Cells

Abstract

In this study the effect of alveolar (AC) or peritoneal (PC) lavage cells from Lewis rats on the mitogen induced proliferation of syngeneic spleen cells was investigated. When total spleen cells were stimulated with PHA (5 μg/ml) or ConA (6 μg/ml), the addition of AC or PC and of their adherent (A) or non-adherent (NA) fractions had dose dependent suppressive effects. After passing the spleen cells through a Sephadex G-10 column, the eluted cells responded poorly to the mitogens. Addition of low numbers (2x10 3 = 10%) AC or NA-AC improved this response, whereas higher concentrations (5 or 10 %) of these cells or any concentration of A-AC, PC, A-PC or NA-PC showed either none or a suppressive effect. The cells which strongly suppress mitogen induced lymphocyte proliferation have macrophage morphology, are adherent, esterase positive, bear Fc receptor for IgG and bind ganglioside coated erythrocytes. NA-AC were further separated into Ia-depleted (Ia -) and Ia-enriched (Ia +) population. The Ia + fraction contained 80 to 90% Ia bearing cells, supported the mitogen induced stimulation of Sephadex G-10 depleted spleen cells and was ineffective in suppression. Interestingly, these cells did not bind ganglioside treated sheep erythrocytes. On the other hand, the Ia-negative NA-AC fraction and particularly the A-AC population strongly expressed the «ganglioside receptor» as well as typical macrophage markers like Fc receptors, latex-phagocytosis and non-specific esterase. Therefore, the «ganglioside receptor» may be a useful marker to define suppressor macrophages.