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ARS Home » Plains Area » Manhattan, Kansas » Center for Grain and Animal Health Research » ABADRU » Research » Publications at this Location » Publication #283438
Title: Vaccines

Author
item SCHULTZ, RONALD - University Of Wisconsin
item McVey, David

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 9/10/2012
Publication Date: 7/1/2013
Citation: Schultz, R.D., Mcvey, D.S. 2013. Vaccines. Book Chapter. Veterinary Microbiology, 3rd Edition:491-500. ISBN:978-0-470-95949-7

Interpretive Summary:

Technical Abstract: Antigens that are processed by antigen-processing cells via the exogenous pathway elicit antibodies. Thus, extracellular bacteria (live or killed), inactivated viral particles, portions (subunits) of virus, and products are processed by the exogenous pathway. Epitopes are presented to the immune system in context of MHC-II by an antigen-presenting cell that secretes IL-1 and little, if any, IL-12. T helper cells (TH2 subset of CD4 lymphocytes) respond to this stimulus by secreting cytokines that trigger an antibody response (IL-4, IL-5, IL-13). Some infectious agents replicate within cells. If the agent multiplies within a mononuclear phagocyte, then antigens are processed by way of the exogenous and/or endogenous pathways. As outlined above with extracellular antigens, antigens of intracellular agents are presented in context of MHC-II, but the antigen-presenting cell secretes IL-1 and IL-12. IL-12 stimulates T helper cells (TH1 subset) while turning off cells of the TH2 subset. TH1 cells secrete INF-gamma, resulting in the activation of mononuclear phagocytic cells. Some of these “intracellular” agents (some viruses, bacteria, fungi) replicate in the cytoplasm of mononuclear phagocytic cells. Antigens from these agents are also processed by the endogenous pathway, as are antigens liberated within nonphagocytic cells, so that epitopes are presented to the immune system in context of MHC-I. Epitopes presented in this fashion are recognized by CD8 cytotoxic lymphocytes. These lymphocytes function by lysing infected targets, i.e., cells expressing epitope-MHC-I complexes.