Experimental investigations on the B and T cell immune response in pulmonary alveolar echinococcosis

Susceptibility/resistance of the intermediate host to alveolar echinococcos is (AE) seems to be based on hitherto unknown immunological mechanisms, pos sibly involving the activation of different CD4(+) T cell immune responses (Th1/Th2). Mice of two strains previously characterized as 'susceptible' (C 57BL/6 J) and 'resistant' (C57BL/10 J) to secondary AE were orally infected with eggs of Echinococcus multilocularis and the course of infection was a nalysed by macroscopical, pathohistological and immunohistochemical examina tions of the lymphocytes and cytokines participating in the peri-parasitic granulomas and by serological examinations of cytokines and E. multilocular is-specific antibodies. Although differences in the extent of parasitic gro wth were seen between the two groups, the composition of the granulomas was quite similar with CD4(+) cells being the dominant lymphocyte subpopulatio n, succeeded by B cells and CD8(+) cells. Interferon (IFN)-gamma-, interleu kin (IL)-2- and IL-4-expressing cells could not be detected in the lesions of the early phase of the infection, possibly indicating the host's immunos uppression, but were present at the end IL-10 was the most prominent cytoki ne throughout the course of the disease. Serological analyses of the cytoki ne concentrations revealed small amounts at the beginning and high levels a t the end of the infection. The pattern of cytokine response was similar fo r IL-4 in both strains but different for IL-2 and IL-10 in the late phase, when the C57BL/10 J strain developed higher levels than the C57BL/6 J strai n. Correspondingly only small amounts of immunoglobulin (Ig)M, IgG1, IgG2a and IgG3 could be detected at the beginning of disease, followed by higher levels at the end. The courses of antibody titres were similar in both grou ps except IgG3, which was more pronounced in the (C57BL/10 J strain. Parasi te-specific IgG2b could neither be detected in the C57BL/6 J nor in the C57 BL/10 J strain by the test system used. The results of the study suggest bo th subsets of CD4(+) T cells (Th1 and Th2) being involved in murine primary alveolar echinococcosis. A strict differentiation of mice in susceptible a nd resistant animals based on the activation of different CD4(+) T cell imm une responses (Th1 'resistant' and Th2 'susceptible') should be avoided.