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Multicellular organisms exist in hostile environments full of dangerous microorganisms. Retrocyclin 2, a θ-defensin analog, acts at cell membranes to hinder viral coat attachment helping to protect multicellular organisms.
Entry of leukocytes into tissues is a key feature of inflammation. New data suggest the polysaccharide heparan sulfate is required for several stages of this entry process.
Insects are capable of fighting viral infection even though they do not have B and T cells. Genetic analysis of drosophila C virus infection provides a glimpse of this unexplored area of innate immunity.
Fcγ receptor–mediated phagocytosis requires Rac and Cdc42 GTPases. New data show that CAPRI, a GTPase-activating protein for Ras, functions as an adaptor for Rac and Cdc42 during phagocytosis and early phases of bacterial immunity.
Lymphocytes continuously recirculate throughout the body. Evidence now suggests chemokine receptor CCR7 actively controls lymphocyte entry into afferent lymphatic vessels.
Physiological tolerance of natural killer (NK) cells to self tissues is believed to require the expression of at least one inhibitory receptor specific for self MHC. This dogma may require revision with the identification of self-tolerant NK cells lacking self MHC–specific receptors.
Stimulation of the vagus nerve via the α7 nicotinic acetylcholine receptor can dampen macrophage function. This anti-inflammatory pathway seems to signal through the Jak2-STAT3 pathway.
Toll-like receptors are crucial in modulating immune responses. Glycogen synthase kinase 3 is involved in Toll-like receptor signaling and regulates the production of proinflammatory cytokines and septic shock.
Cells of the innate and adaptive immune systems often require signals emanating from diverse cell surface receptors for full activation. For dendritic cells, synergistic stimulation by different pairs of Toll-like receptors provides the host with a mechanism to react rapidly and specifically to different pathogens.
Contrary to results of previous studies using high frequencies of T cell receptor–transgenic T cells, new data indicate that when naive precursor frequencies approach endogenous levels, CD8+ effector and central memory T cell lineage commitment is fixed.
Structural studies of CD1d presentation of α-galactosylceramide have shown that the lipid component fits snugly in the cleft, whereas the galactosyl head group protrudes upward, with key contact points between CD1d and the antigen conserved between mouse and human structures.
After leaving lymphoid tissues, do T cells receive additional signals for survival and differentiation at effector sites? A unique cell population in the intestinal lamina propria may provide such a signal via the costimulatory molecule CD70.
Tumors that develop in immunocompetent hosts show reduced immunogenicity because of selective pressure to escape destruction by immune cells. Type I interferons are involved in shaping this evasive response but, unexpectedly, tumor cells are not the main targets of these interferons.
Notch is essential for T lineage cell differentiation. Three new papers look at when Notch signaling is required and how it affects different cell types.
