Effects of levamisole, DTC and low-dose mechlorethamine on humoral response of SRBC-immunized rabbits exposed to cold stress.

The experiments were carried out on normothermal rabbits and rabbits exposed to cold stress (hypothermia). The animals of the latter group were submerged in ice-water for 20 s and then placed in a freezer at -15 degrees C for 8 min until their body temperature dropped by 3 degrees C. Both the normothermal and hypothermal rabbits were immunized i.p. with 3 ml of 10% sheep red blood cells (SRBC). Levamisole (2 mg/kg), DTC (sodium diethyldithiocarbamate, 20 mg/kg) or mechlorethamine (mustine; 5 micrograms/kg) were injected i.v. three times at 24-h intervals. The number of PFC, total (19S + 7S) and 2-mercapthoethanol resistant (7S) serum haemagglutination titres were determined. It was found that, in normothermal rabbits, all three agents potentiated the number of plaque-forming cells (PFC); the impact of DTC was the strongest, while the weakest influence was observed for mechlorethamine. Furthermore, DTC increased anti-SRBC haemagglutinin titre, whereas mechlorethamine did not. Levamisole, on the other hand, reduced total serum haemagglutinin titre. Cold stress reduced humoral response to SRBC, which was reflected in the decreased number of PFC and serum haemagglutination titres (19S + 7S and 7S). Each agent showed a different way of action. Pretreatment with DTC prevented the immunosuppression caused by cold stress, while levamisole and mechlorethamine only reduced the immunosuppressive effect.