Antigen-specijic proliferative responses and cytokine production were measured in lymphocytes taken from inbred NIH mice infected with different isolates of Trichinella spiralis. Stimulation with muscle larval homogenate antigen produced high proliferative responses, cells responding more strongly to antigen from one isolate (London-L) than to antigens ofthe other two isolates (Spanish-S and Polish-P). Antigen from the P-isolate elicited relatively poor responses. There was considerable, although variable, cross reactivity between isolate antigens and this was rejected in prolifEration to heterologous stimulation. When pulsed with the mitogen Concanavalin A (Con-A) mesenteric lymph node cells ( M L N C ) produced IFN-gamma on day four post infection but not on day eight. In contrast, production of IL-4 and IL-5 was greatest on day eight. Differences were seen in levels of cytokine production between cells taken from mice infected with different isolates. These data show a sequential activation of Thl and Th2 cells during infection with T. spiralis isolates, and suggest that the level ofactivation of each Th subset is influenced by the antigenic characteristics of each isolate.
The influence of nonspecific immunomodulation on the course of experimental infection was examined in larval cestodosis (Mesocestoides corti) and ascaridosis (Ascaris suum) in mice. Immunosuppressive treatment (with azathioprine or hydrocortisone) resulted in a decrease of resistance in both models. The subsequent administration of T-activin to immunosuppressed mice led to the restoration of resistance to a level equal to that of untreated control mice. The administration of different immunomodulators partially protected mice against M. corti (T-activin. thymomodulin) or A. suum (T-activin. thymomodulin. thymosin fr.5. bursa-activin) infection. The protective effect of different treatments did not correlate with the level of specific antibody in the sera of infected mice. These results, which confirmed the decisive role of T-cell immunity in the resistance to the helminth infections, raise the possibility of the use of immunomodulators (thymic preparations) in the immunoprophylaxis of helminthoses.
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