Lymphatic System and Body Immunity Help (page 2)

By — McGraw-Hill Professional
Updated on Aug 18, 2011

Cell-Mediated Immunity

Cell-mediated immunity is another mechanism of specific immunity. In this case, cells provide the main defensive strategy. Lymphocytes, circulating in the blood and found in lymphoid tissues, (T lymphocytes and B lymphocytes) become sensitized to an antigen, attach themselves to that antigen, and destroy it. T lymphocytes produce cell-mediated immunity. Upon interacting with a specific antigen they become sensitized and differentiated in several types of daughter cells.

B lymphocytes produce antibody-mediated immunity. B lymphocytes become sensitized to an antigen, proliferate, and differentiate to form clones of daughter cells.

Other Components of the Immune System

Other components of the immune system are:

  • Cytokines (interferons, chemotactic factors, macrophage-activating factors, migration-inhibiting factors, transfer factors): Chemical messengers used by the immune system to enhance immune response.
  • Complement system: Enzyme precursors that aid immune response by causing lysis of invading cells, attract and enhance the action of phagocytes, enhance inflammation, and neutralize viruses.

Transfusion Rejection Reaction

Red blood cells have large numbers of antigens present on their cell membranes; these can initiate antibody production, and therefore antigen-antibody reactions. One of the groups of antigens most likely to cause blood transfusion reactions is the ABO system. Antigens are inherited factors present on the RBC membranes at birth. If the recipient of a blood transfusion and the donor are improperly matched the antigen-antibody reaction (transfusion reaction) occurs (see Table 17.3) causing RBC to clump, rupture, and hinder the flow of blood.

Another group of antigens associated with blood is the Rh system. Rh antigens are present on the red blood cell membranes of about 85% of the population. These people are classed as Rh positive (Rh+). The remaining 15% are classed as Rh negative (Rh-). Rh- individuals do not develop antibodies against Rh antigens until they are exposed to Rh+ blood.

Practice problems for these concepts can be found at:

Lymphatic System and Body Immunity Practice Problems

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