IL-33 (IL-1F11) is a recently described member of the IL-1 family of cytokines that stimulates the generation of cells, cytokines, and Igs characteristic of a type 2 immune response. IL-33 mediates signal transduction through ST2, a receptor expressed on Th2 and mast cells. In this study, we demonstrate that IL-33 and ST2 form a complex with IL-1R accessory protein (IL-1RAcP), a signaling receptor subunit that is also a member of the IL-1R complex. Additionally, IL-1RAcP is required for IL-33-induced in vivo effects, and IL-33-mediated signal transduction can be inhibited by dominant-negative IL-1RAcP. The implications of this shared usage of IL-1RAcP by IL-1(α and β) and IL-33 are discussed.

We report that dissemination of Mycobacterium tuberculosis in the mouse is under host control and precedes the initiation of T-cell immunity. Nine to eleven days after aerosol inoculation, M. tuberculosis disseminates to the pulmonary lymph nodes (LN), where M. tuberculosis-specific T cells are detected 2 to 3 days thereafter. This indicates that the initial spread of bacteria occurs via lymphatic drainage and that the acquired T-cell immune response is generated in the draining LN. Dissemination to peripheral sites, such as the spleen and the liver, occurs 11 to 14 days postinfection and is followed by the appearance of M. tuberculosis-specific T cells in the lung and the spleen. In all cases studied, dissemination to the LN or the spleen preceded activation of M. tuberculosis-specific T cells in that organ. Interestingly, bacteria disseminate earlier from the lungs of resistant C57BL/6 mice than from the lungs of susceptible C3H mice, and consequently, C57BL/6 mice generate an immune response to M. tuberculosis sooner than C3H mice generate an immune response. Thus, instead of spreading infection, early dissemination of M. tuberculosis may aid in the initiation of an appropriate and timely immune response. We hypothesize that this early initiation of immunity following inoculation with M. tuberculosis may contribute to the superior resistance of C57BL/6 mice.

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