Figure 50-1. The immune system response to a virus.

Figure 50-1The immune system response to a virus

(1) Virus bearing an antigenic epitope. (2) Processing of antigen to fragments. (3) Presentation of antigen (Ag) to T cells (on the infected cell surface) and B cells (free antigenic pieces or viruses). (4 and 5) Regulator T cells help (4) or suppress (5) both B and T effector responses. (6) Antigen-specific cytotoxic (killer) T cells. (7) T cells (helper as well as cytotoxic) produce lymphokines. (8) Some lymphocytes (both T and B) activated by antigen differentiate into a long-lived pool of memory cells responsible for rapid, secondary response to the same antigen. (9) Antibody combines with antigen (neutralization, elimination). (10 and 11) Products of T cells activate macrophages for killing of ingested virus (10) and natural killer cells (11) for nonspecific cytotoxicity against virus-infected cells. (12) Interferons are produced for protection of surrounding cells against virus infection. (13) Complexing of antibody with virus (opsonization) increases the engulfment of the virus by phagocytes and can neutralize virus. (14) Binding of antibody to infected target cells activates the antibody-dependent cytotoxic cell (ADCC). (15) Complement enzymatic cascade is activated by antigen-antibody complex (in this case, the antigen is on the cell surface). (16) Antibody binds to immunoglobulin receptors on basophils and mast cells.

From: Chapter 50, Immune Defenses

Cover of Medical Microbiology
Medical Microbiology. 4th edition.
Baron S, editor.
Copyright © 1996, The University of Texas Medical Branch at Galveston.

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