Innate immunity

Women are more resistant to hepatocellular carcinoma (HCC) than men despite equal exposure to major risk factors, such as hepatitis B or C virus infection. Female resistance is hormone-dependent, as evidenced by the sharp increase in HCC incidence in postmenopausal women who do not take hormone replacement therapy. In rodent models sex-dimorphic HCC phenotypes are pituitary-dependent, suggesting that sex hormones act via the gonadal-hypophyseal axis. We found that the estrogen-responsive pituitary hormone prolactin (PRL), signaling through hepatocyte-predominant short-form prolactin receptors (PRLR-S), constrained TNF receptor-associated factor (TRAF)-dependent innate immune responses invoked by IL-1β, TNF-α, and LPS/Toll-like receptor 4 (TLR4), but not TRIF-dependent poly(I:C)/TLR3. PRL ubiquitinated and accelerated poststimulatory decay of a "trafasome" comprised of IRAK1, TRAF6, and MAP3K proteins, abrogating downstream activation of c-Myc-interacting pathways, includin...

The plasma membrane glycoprotein receptor CD163 is a member of the scavenger receptor cystein-rich (SRCR) superfamily class B that is highly expressed on resident tissue macrophages in vivo. Previously, the molecule has been shown to act as a receptor for hemoglobin-haptoglobin complexes and to mediate cell-cell interactions between macrophages and developing erythroblasts in erythroblastic islands. Here, we provide evidence for a potential role for CD163 in host defense. In particular, we demonstrate that CD163 can function as a macrophage receptor for bacteria. CD163 was shown to bind both Gram-positive and -negative bacteria, and a previously identified cell-binding motif in the second scavenger domain of CD163 was sufficient to mediate this binding. Expression of CD163 in monocytic cells promoted bacteria-induced proinflammatory cytokine production. Finally, newly generated antagonistic antibodies against CD163 were able to potently inhibit cytokine production elicited by bacter...

The mammalian immune system has evolved several mechanisms that allow bacterial and viral infections to be successfully fought. Animal cells are able to recognize viral infection and this recognition is dependent on the presence of intracellular sensors that instantly identify danger signals and initiate signal cascades leading to an effective antiviral response. Several host proteins have been identified as intracellular sensors, namely: Toll-like receptors, RIG-I-like receptors, AIM2-like receptors and DAI, DNA-dependent activator of IFN regulatory factor. They recognize and bind viral genomic nucleic acids and all their replicative intermediates. Receptor-ligand interaction leads to activation of specific metabolic pathways that include synthesis and release of type I interferons and proinflammatory cytokines. These mediators are in turn responsible for synchronizing mechanisms of innate and adaptive antiviral immunity. They are crucial for blocking viral replication, preventing ...

NK cells are the major lymphocyte subset of the innate immune system that mediates antiviral and anti-tumor responses. It is well established that they develop mechanisms to distinguish self from non-self during the process of NK cell education. Unlike T and B cells, natural killer cells lack clonotypic receptors and are activated after recognizing their target via germline-encoded receptors through natural cytotoxicity, cytokine stimulation, and Ab-dependent cellular cytotoxicity. Subsequently, they utilize cytotoxic granules, death receptor ligands, and cytokines to perform their effector functions. In this review, we provide a general overview of human NK cells, as opposed to murine NK cells, discussing their ontogeny, maturation, receptor diversity, types of responses, and effector functions. Furthermore, we also describe recent advances in human NK cell biology, including tissue-resident NK cell populations, NK cell memory, and novel approaches used to target NK cells in cancer immunotherapy.