Stimulatory effect of 5-azacytidine on 7S antibody production on rats

Immunomodulatory properties of monoclonal anti-Thy-1.2 antibody in vivo

Monoclonal mouse anti-Thy-1.2 antibody of IgG3 isotype (MTA) inhibits in a significant and long-term manner the regional graft-versus-host reaction (GVHR) when administered to donors as well as to recipients. The process of sensitization in the reaction of delayed type hypersensitivity to SRBC (DTH) is, on the other hand, suppressed only if MTA is administered immediately prior to sensitization. If the time interval between the injection of MTA and of SRBC is extended, the resulting DTH is stimulated. Similarly, the titers of total Ig against SRBC are decreased only if MTA is administered shortly before immunization. Contrasting effects of MTA on the production of IgM and IgG were observed. While the production of IgG was inhibited even after the time interval between the administration of MTA and immunization had been increased, the production of IgM antibodies was stimulated. In recipients of allogeneic Sarcoma I treated with MTA, the primary growth of the tumor is enhanced and the percentage of permanent progressors is increased. Mechanisms of MTA activity are discussed.

Inhibitory effects of 5-azapyrimidine nucleosides on cellular immunity

The effect of 5-azacytidine (5-AzCR) and 5-aza-deoxycytidine (5-AzCdR) on the survival of skin grafts in mice and rats, the action of these drugs on regional GVH reaction, as well as the formation of haemopoietic colonies (CFU-5) in the spleen were studied. Both drugs prolonged the life span of skin grafts when administered 24 hr before transplantation, or on the 4th post-transplantation day. However, they were little effective when injected 24 hr after skin grafting, or after induction of the regional GVHR. Following intraperitoneal administration, they inhibited CFU-5 formation. Two-hour incubation in vitro of cells with 5-AzCR significantly reduced their GVH reactivity and capacity to form CFU-5; 5-AzCdR under the same conditions was ineffective.