4. Immune Response
  • Important Components:
    • Antigen-presenting cells (APCs)
APCs or antigen presenting cells preprocess and present antigen to lymphocytes
Antigen processing: The mechanism by which foreign antigens are taken into antigen- presenting cells (APCs) and broken up.  Part of the antigen is then displayed (presented) on the surface of the APC next to a histocompatibility or “self” antigen, activating T lymphocytes and cell- mediated immunity. T lymphocytes are unable to recognize or respond to most antigens without APC assistance. The most active APCs are macrophages, B cells, and dendritic cells.
    • Immune activated B-cell produces antibody with unique antigen-binding site (idiotype)
    • Secondary antibody responses involve clonal expansion
    • Response dependent on:
      • Antigen
      • Dose
      • Route of entry
      • Synergistic substances
      • genetic background of individual
graphic
Fig. 5-1 Schematic of the two arms of the immune system: humoral immunity (left), mediated by soluble antibody proteins produced by B lymphocytes, and cellular immunity (right), mediated by T lymphocytes. Antibodies participate in immunity either by directly neutralizing extracellular microbes or by activating complement and certain effector cells (polymorphonuclear neutrophils [PMNs] and macrophages) to kill microorganisms. T cells can either directly lyse targets (cytotoxic T cells) or orchestrate the immune response of other cells to clear invading microbes by producing soluble protein mediators called cytokines (helper T cells).
 
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