Antibody response against Litomosoides carinii and the distribution of bound antibodies on microfilariae from the different internal organs of cotton rats.

The courses of IgG and IgM antibody levels against adult worm and microfilarial antigen were determined in isogenetic cotton rats infected quantitatively with Litomosoides carinii. Against both antigens, IgG as well as IgM, antibody levels exceeded significantly those of noninfected animals, and the IgG levels were generally higher than the IgM levels. The total antibody production was depressed transiently 8 weeks p.i. by the appearance of microfilariae in the peripheral blood. A second transient depression occurred two weeks earlier against microfilarial antigen than it occurred against adult worm antigen. At 3 different times after the infection, the amount of adsorbed antibodies was assessed on adult worms and on microfilariae, which were isolated from blood and by a specially developed method from the internal organs. The percentual distribution of microfilariae in the different organs and blood changed during patency. In spleen, kidney, and lung a continuous increase was observed, whereas in heart and liver the percentage initially increased, and then decreased. The opposite course was seen in blood. Most antibodies adsorbed on the surface of microfilariae and adult worms belonged to the IgM class. Predominantly, the antibodies were detected on organ microfilariae, particularly on those in spleen and kidney, while blood microfilariae had lower amounts of bound antibodies. Furthermore, by complement fixation, no common antigens could be detected on the surface of host cells and the different L. carinii stages.

T-cell dependent and T-cell independent immune response in normal and in with Litomosoides carinii infected cotton rats.

The immune responses to SRBC and LPS were examined in immunized and non-immunized inbred cotton rats at different times after an infection with Litomosoides carinii. During the infection, the T-cell dependent immune response to SRBC was significantly suppressed in non-immunized animals as compared to non infected controls. In contrast, after immunization with SRBC the antibody levels of infected animals were significantly higher in three of five events. At the onset of patency the response to SRBC was significantly depressed transiently in immunized animals. A corresponding depression could be provoked by injections of isolated microfilariae as well as by FCS in immunized animals, infected and non-infected. The level of the antibodies was dependent on the density of microfilariae in the peripheral blood. The T-cell independent response to LPS was equal in non-immunized infected animals as in controls. After immunization with LPS during prepatency and at onset of patency a distinct but commensurate reaction was observed. Only after immunization at the peak of patency, the immune response of infected animals was significantly suppressed. In general, the antibody levels to LPS were not influenced by the microfilaremia.