Immune responses to naturally acquired Pneumocystis carinii in gene disruption mutant mice

Dose-dependent activation of lymphocytes in endotoxin-induced airway inflammation

Recruitment of neutrophils to lung tissue and airspaces is a hallmark of inflammatory events following inhalation of endotoxins. We studied the role of different lymphocyte subsets in this inflammation, which is assumed to primarily involve the innate immune system. Inhalation of aerosolized Escherichia coli lipopolysaccharide (LPS) in mice induced a dose-dependent increase in neutrophils in bronchoalveolar lavage fluid, reaching a maximum after 12 h at a low dose and after 24 h at a high dose. Profiles of gene expression in lung tissue indicated an early (2 h) and transient onset of proinflammatory cytokines and chemokines by a low dose of LPS, while a high dose caused more delayed and sustained (6 to 12 h) activation. Gamma interferon, interleukin-2 (IL-2), RANTES, and the alpha chain of the IL-2 receptor were not expressed at a low dose, whereas a high dose of LPS induced a strong expression of these genes, indicating a dose-dependent activation of T cells. A similar pattern was observed for IL-17, supporting a contribution of T cells to the neutrophilic inflammation only at high-dose exposure to LPS. The involvement of lymphocytes in the inflammatory response was further studied using mice with functional deficiencies in defined lymphocyte subsets. Both gammadelta T-cell- and B-cell-deficient mice displayed a response similar to that of the corresponding wild-type strains. Selective depletion of NK cells by in vivo administration of the pk136 antibody did not significantly affect the recruitment of neutrophils into airspaces. Thus, neither NK cells, B cells, nor gammadelta T cells appeared to participate in the host response, suggesting that among the lymphocyte subsets, alphabeta T cells are exclusively involved in endotoxin-induced airway inflammation.

Effect on parasite eradication of Pneumocystis carinii-specific antibodies produced in the presence or absence of CD4(+) alphabeta T lymphocytes

The contribution of specific antibodies (Ab) to successful clearance of Pneumocystis carinii from host pulmonary tissues has received increasing attention. Sera collected from diseased recombinase-activating gene (RAG)-1(-/-), TCRbetaxdelta(-/-), TCRbeta(-/-) and Abeta(-/-) mutants as well as from aerogenic parasite-exposed (aero) and intranasally (i. n.) infected C57BL/6 mice were transferred to RAG-1(-/-) mutants inoculated with freshly isolated parasites. All sera, except for RAG-1(-/-) serum, contained P. carinii-specific Ab of varying isotype concentrations. Four weeks after serum treatment pulmonary parasite numbers were reduced slightly by Abeta(-/-) and C57BL/6-aero sera, and markedly by TCRbeta(-/-) and C57BL/6-i.n. sera. Our data reveal: (1) T cells are essential, and CD4(+) T cells are important for formation of protective Ab; (2) at least in the absence of alpha beta T cells, gamma delta T cells provide help for protective Ab. In vitro treatment of bronchoalveolar lavage cells with the different sera largely led to comparable results. Opsonizing Ab impeding parasite attachment to host cells, as well as Ab possibly neutralizing parasite-secreted products were implicated. Furthermore, serum components other than Abappear to participate in resistance to fungal manifestation.