Macrophage-mediated killing of splenic lymphocytes in adjuvant-induced arthritis

After 72 hrs in culture, unseparated spleen cells from rats with adjuvant-induced arthritis (AA) stimulated with high concentrations of Con A (>0.63 g/ml) leaked more lactate dehydrogenase (LDH) than did either unstimulated cultures or cultures stimulated with lower concentrations of Con A. This reflects and increase in dead or dying cells at concentrations of Con A >0.63 g/ml. Since Con A did not increase LDHlleakage in macrophage-depleted cultures of AA splenocytes, the decreased viability in unseparated, Con A-stimulated cultures appears to be a macrophage-dependent phenomenon. Since the increase in LDH release at high concentrations of Con A paralleled the decrease in ³H]-thymidine incorporation, these results suggest that Con A (>0.63 g/ml) induces macrophages from AA rats to kill splenic lymphocytes in culture.