Microbial heat shock protein 65 attenuates airway hyperresponsiveness and inflammation by modulating the function of dendritic cells.

Heat shock proteins (HSPs), produced in response to stress, are suppressive in disease models. We previously showed that Mycobacterium leprae HSP65 prevented development of airway hyperresponsiveness and inflammation in mice. Our goal in this study was to define the mechanism responsible for the suppressive effects of HSP. In one in vivo approach, BALB/c mice were sensitized to OVA, followed by primary OVA challenges. Several weeks later, HSP65 was administered prior to a single, provocative secondary challenge. In a second in vivo approach, the secondary challenge was replaced by intratracheal instillation of allergen-pulsed bone marrow-derived dendritic cells (BMDCs). The in vitro effects of HSP65 on BMDCs were examined in coculture experiments with CD4(+) T cells. In vivo, HSP65 prevented the development of airway hyperresponsiveness and inflammation. Additionally, Th1 cytokine levels in bronchoalveolar lavage fluid were increased. In vitro, HSP65 induced Notch receptor ligand Delta1 expression on BMDCs, and HSP65-treated BMDCs skewed CD4(+) T cells to Th1 cytokine production. Thus, HSP65-induced effects on allergen-induced airway hyperresponsiveness and inflammation were associated with increased Delta1 expression on dendritic cells, modulation of dendritic cell function, and CD4(+) Th1 cytokine production.

Characterization and functional studies of the murine T-lymphocyte response to Mycobacterium leprae antigen.

Mice were immunized with Mycobacterium leprae in incomplete Freund's adjuvant, and sensitized lymphocytes were obtained from draining lymph nodes. The lymphocytes thus obtained proliferated specifically in vitro in the presence of M. leprae antigen, and this response was shown to be both T-cell and macrophage dependent. T-cell blasts generated in vitro in response to M. leprae antigen were grown in the presence of interleukin-2 (IL-2). The proliferative response of these blasts to M. leprae antigen was strictly dependent on the presence of syngeneic spleen cells as antigen-presenting cells. M. leprae-immune F1 blasts responding to the antigen in the context of either parental H-2 haplotype-bearing accessory cell could be obtained by positive selection from an F1 hybrid-responding cell population. By means of flow microfluorometry the T-cell phenotype of the M. leprae-specific T-cell blasts was found to be Thy-1+ and to be composed of Lyt-1+ and Lyt-2+ subpopulations. Functionally, the blasts were shown to transfer delayed-type hypersensitivity locally to non-immunized recipients and to have cytolytic activity. Limiting dilution analysis showed the frequency of M. leprae-responding cells from blasts grown in IL-2 to be approximately 1/333.