Animals have natural barriers and substances which help to prevent infections. Animals have natural barriers and substances which help to prevent infections with micro-organisms and parasites. The skin and mucus-containing secretions act as barriers, and proteolytic enzymes (digestive enzymes which break down protein) present in body fluids have the ability to destroy some invading organisms. In addition to this, cells with specific innate immune functions rapidly respond to invading organisms to destroy them. These cells are primarily of two types: monocytes (especially macrophages) and polymorphonuclear leucocytes. Both of these can ingest micro-organisms by a process known as “phagocytosis” and destroy them. They also synthesize and secrete many substances, including cytokines and enzymes, which protect against infections and promote the development of the immune response.
protection against parasites. The function of circulating IgD is unclear. Immunoglobulins are produced and secreted by B-lymphocytes.
Antibodies bind specifically to non-self organisms and substances. This often results in inactivation of undesired properties. Antigen-antibody complexes are removed from the body by various processes and antibody-coated micro-organisms are particularly susceptible to phagocytosis by macrophages and other cells. After interacting with an antigen, antibodies trigger a range of immunobiological mechanisms which protect against infections and other undesirable effects.
Antibodies bind specifically to non-self organisms and substances. This often results in inactivation of undesired properties. Antigen-antibody complexes are removed from the body by various processes and antibody-coated micro-organisms are particularly susceptible to phagocytosis by macrophages and other cells. After interacting with an antigen, antibodies trigger a range of immunobiological mechanisms which protect against infections and other undesirable effects.
Cell-mediated immunity is mediated by T-lymphocytes. Antigen-specific T-cells are produced, which interact with antigens to mediate a number of immunobiological functions. One example of this is the production of cytotoxic cells that specifically “kill” unwanted micro-organisms or cells. A third class of lymphocyte, known as large granular lymphocytes or natural killer (NK) cells, also destroy non-self cells and micro-organisms. The acquired immune response complements the innate response to provide a specific, very efficient defence system.
CONTROLLING THE DEVELOPMENT OF ACQUIRED IMMUNITY:
The acquired immune system is tightly controlled. B-lymphocytes that secrete antibodies are strongly influenced by T-cells which can either “help” the response or suppress it. Such T-cells secrete cytokines and other potent, biologically active molecules which enhance or inhibit B-cell activation, maturation, and ability to secrete appropriate immunoglobulin. B-cells (and other cell types) also secrete cytokines which modulate immunity. In particular, Interleukins 1,2,4,6,10,12,13,14,15, and 16, •-interferon, and transforming growth factor β influence the development and modulation of the acquired immune response. IL-12 is a potent stimulator of NK cells.