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The Immune System

  • The first line of defense is barrier to entry. The skin, mucus membranes and tears are barrier defenses.
  • The second line of defense includes nonspecific cellular defenses such as neutrophils, macrophages and natural killer cells. Proteins such as complement and interferon also play a role in nonspecific defense.
  • B cells are produced and mature in the bone marrow. B cells are responsible for humoral immunity, which is mediated by antibodies secreted by plasma cells.
  • T cells mature in the thymus and are responsible for cell-mediated immunity.
  • Cytotoxic T cells destroy cells that are infected by a pathogen or that are abnormal.
  • Helper T cells assist in activating the production of antibodies by B cells and by stimulating cytotoxic T cells.
  • Antigens are presented to T cells by Major Histocompatibility Complex (MHC) Molecules on the surface of cells.
  • Passive immunity is conferred when an individual is given pre-formed antibodies. Active immunity requires the stimulation of a person's own immune system.

The Immune System

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

AP Biology Intro