Thus, the surface proteins of C. difficile might not be related
to the varying virulence of the currently epidemic ribotypes 027, 001 and 106. The large volumes of toxin produced by the hypervirulent ribotype 027 might elicit a greater immune response in vivo because of extensive damage leading to chronic inflammation, but this could not be identified from the results obtained here. However, it remains that surface-associated proteins of C. difficile are able to trigger inflammatory responses and can directly interact with the immune system along with its toxins. Further, the lack of correlation between the magnitude of the immune response and ZD1839 clinical trial the C. difficile strain from which the surface-associated proteins were extracted enhances their suitability as components for a vaccine against CDI. ”
“NK cells are important mediators of the early defense. In mice, immature and mature NK (mNK) cells constitutively express the TNF receptor family member CD27; however, mNK cells eventually lose CD27 expression and become BKM120 datasheet resting NK cells. Interaction of CD27 with its ligand, CD70, enhances proliferation and effector functions of NK cells. We used mice that constitutively express CD70 on B cells (CD70-Tg) to study the in vivo effects of continuous triggering of CD27 on NK cells. Continuous CD70-CD27 interaction resulted in strongly down-modulated CD27 expression on NK cells and gradually reduced absolute
NK cell numbers. This reduction was most prominent in the mNK cell subpopulation and was at least partially due to increased apoptosis. Residual NK cells showed lower expression of activating Ly49 receptors and normal (liver) or decreased (spleen) IFN-γ production.
Nevertheless, NK cells from CD70-Tg mice displayed higher YAC-1 killing capacities. CD70-Tg NK cells exhibited up-regulated expression of NKG2D, Dichloromethane dehalogenase which is in accordance with the increased YAC-1 lysis, as this is mainly NKG2D-dependent. Taken together, this study is the first to demonstrate that continuous CD70 triggering of CD27 on NK cells in vivo results in a severe reduction of NK cells. On a single cell basis, however, residual NK cells display enhanced cytotoxicity. NK cells are large granular lymphocytes of the innate immune system that play a crucial role in the early host defense 1, 2. Upon activation, they directly eliminate target cells through exocytosis of perforin- and granzyme-containing granules, or by Fas ligand (CD178) or TRAIL pathways 3–7. NK cells also produce cytokines and chemokines, which enable them to recruit non-specific haematopoetic cells, activate dendritic cells and prime adaptive lymphocytes 8–11. As such, NK cells bridge between innate and adaptive immunity. The functional behaviour of NK cells is regulated by the engagement of a broad array of activating and inhibitory cell membrane receptors (reviewed in Lanier 12). The BM is considered to be the main site for NK cell development 13–16.