title: The effects of a new phthalazine derivative (MDL 899) on human lymphocyte functions.
abstract: MDL-899 is new phthalazine derivative which has been developed as a substitute for hydralazine, which has several undesirable effects, in the treatment of hypertension. The effects of MDL-899 on human lymphocyte functions are analyzed. This drug inhibited in a dose-related fashion the blastogenesis of lymphocytes upon PHA and Con A activation and down-regulated the activation of allogeneic mixed lymphocyte reactions (MLR). On the contrary the drug enhanced the activation of autologous MLR of non T/T type. This effect was five times higher on cells which carried the HLA DR 4 phenotype. The above reported observations suggest that MDL-899, as well as hydralazine, affects the in vitro responsiveness of human lymphocytes mostly in subjects with HLA-DR 4 phenotype. Whether the impact of MDL-899 on immune function gives rise to a lupus like syndrome is not known. For this reason further studies are warranted to assess its long-term in vivo effects.
mesh_terms: D000911:Antibodies, Monoclonal; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D006801:Humans; D006830:Hydralazine / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects*; D007959:Lymphocyte Culture Test, Mixed; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology*; D008934:Mitogens; D011724:Pyridazines / Q000494:pharmacology*; D012397:Rosette Formation
chemical_list: D000911:Antibodies, Monoclonal; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; D008934:Mitogens; D011724:Pyridazines; D006830:Hydralazine; C038811:mopidralazine