ABSTRACT
Mice injected with 10(5) culture trypomastigotes (CT) survived the 30-day observation period while those injected with the same number of bloodstream trypomastigotes (BT) died in 10 +/- 1 days. As early as 24 h after injection of CT the mice displayed an increased resistance to Trypanosoma cruzi as indicated by an increased longevity when challenged with lethal doses of BT. The phagocytic activity of mice injected 24-72 h earlier with CT is increased, while that of mice injected with BT is decreased. The data suggest that parasite factors acting on the early phase of the immune response play a role in the outcome of the infection.
Subject(s)
Antibodies, Protozoan/biosynthesis , Chagas Disease/immunology , Animals , Female , Immune Tolerance , Immunization , Male , Mice , Mice, Inbred CBA , Phagocytosis , Spleen/cytology , Time Factors , Trypanosoma cruzi/immunologyABSTRACT
The effect of Escherichia coli enterotoxin STa on the primary and secondary immune response in F1 (CBA x C57 B1/10) mice immunized against sheep red blood cells (SRBC) was investigated. Modulating action on the IgM and IgG response was found to be dependent on the dose-time administration of the toxin. Immunosuppression of the primary response on the 4th day after immunization was observed when the toxin was injected 15 min before the SRBC, followed by immunostimulation on the 6th day after antigen (Ag) injection. Moreover, toxin administration 48 h before SRBC caused immunosuppression of the primary immune response on the 4th and 6th days. On the other hand, the IgM and IgG secondary immune response, determined 6 days after boosting, was greatly enhanced by toxin administration 15 min before priming (day 0) or boosting (day 26) and 48 h before priming. The same response was suppressed by toxin administration 48 h before booster antigen injection.
Subject(s)
Antibody Formation/drug effects , Bacterial Toxins/pharmacology , Enterotoxins/pharmacology , Animals , Bacterial Toxins/isolation & purification , Dose-Response Relationship, Drug , Enterotoxins/isolation & purification , Escherichia coli/growth & development , Escherichia coli Proteins , Female , Hemolytic Plaque Technique , Immunoglobulin G/analysis , Immunoglobulin M/analysis , Male , Mice , Mice, Inbred StrainsABSTRACT
The Biozzi "high" (BH) and "low" (BL) responder mice (Selection III) differed in their susceptibility to Trypanosoma cruzi. The BH strain responded quickly to the infection, similar to the reaction of (CBA X C57B1/10)F1 mice but in contrast to the susceptible BL strain. We suggest that the IgG response mounted by the host during the prepatent period of the infection is crucial to the outcome of the infection.
