Immunomodulation by RS-2131, a new non-steroidal antiinflammatory drug

The immunomodulatory properties of RS-2131, 2-[4-(2-oxocyclohexylidenemethyl)phenyl]propionic acid, were studied using normal and autoimmune mice. RS-2131 suppressed the Arthus-type footpad reaction in BALB/c mice when administered orally at the time of immunization with sheep red blood cells, in contrast to indomethacin. This drug also suppressed the direct plaque-forming cell response against sheep erythrocytes in BALB/c mice. Under the same experimental conditions, the percentage ratio of Lyt 2+ cells to Thy 1.2+ cells were increased in the spleen cells. When used in non-immunized normal BALB/c mice, however, RS-2131 produced no effect on the ratio of Lyt 2+ cells to Thy 1.2+ cells in the spleen cells and on the percent distribution of T lymphocyte subsets. In MRL/Mp-lpr/lpr (MRL/lpr) mice, which have been known as a model of autoimmune disease, Lyt 2 cells in the thymus and the lymph node increased on oral treatment with RS-2131. These findings suggest that this drug may induce suppressor T cells only when the immune response in host animals is increased and then results in inhibition of immune responses in mice.