1. Some general features of immune responses. A
Some general features of immune responses. A. Steps from recognition to action. (1) Binding antigens to antigen receptors generates internal signals. (2) Antigen-stimulated cells release inflammatory signals that activate other cells. (3) Effector cells attack the source of antigens with toxic chemicals and engulf debris. B. Toll-like receptors (TLRs). Shown are examples of antigen receptors present on innate immune cells that recognize molecules specific to microbes and viruses. TLR-4 on the outside of the cells binds lipopolysaccharides (LPS) produced by gram-negative bacteria, whereas TLR-9 in endosomes recognizes DNA from bacteria and viruses. Receptor binding results in the activation of genes for inflammatory cytokines. C. Interferons protect against viral infection. Any cell infected with a virus responds by producing interferons. These cytokines bind to neighboring cells and initiate reactions that help resist viral infection. D. Complement proteins identify cells for attack. The attachment of complement protein C3b to the surface of cells induces several responses, including the assembly of the membrane-attack complex (MAC), that pokes a hole in the cell membrane, resulting in cell lysis. Host cells protect themselves by expressing membrane proteins that inactivate C3b.
Source: IMMUNE SYSTEM, The Big Picture: Histology
Citation: Ash R, Morton DA, Scott SA. The Big Picture: Histology; 2017 Available at: Accessed: October 10, 2017
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