CCA [N-(2-carboxyphenyl)-4-chloroanthranilic acid disodium salt], a newly developed immunomodulating drug, suppresses T-cell activation by acting on macrophages.

The cellular mechanism of action of a newly developed drug, CCA, N-(2-carboxyphenyl)-4-chloroanthranilic acid disodium salt, on PHA-, autologous mixed lymphocyte reaction (AMLR)-, and phorbol myristate acetate (PMA)-stimulated T-cell proliferation was investigated. Addition of 50 micrograms of CCA per milliliter suppressed PHA- and AMLR-stimulated T-cell proliferation. In contrast, CCA failed to suppress PMA-stimulated macrophage-depleted T-cell proliferation. After treatment of T cells or macrophages with CCA for 12 h, recombined T cells and macrophages were stimulated with phytohemagglutinin. [3H]Thymidine incorporation by T cells was suppressed when macrophages but not T cells were treated with CCA. These results indicate that CCA suppresses T-cell proliferation by acting on macrophages. The mechanism involved in this suppression of CCA was due to the loss of Ia antigen on macrophages and the loss of interleukin-1 (IL-1) secretion from macrophages.