Innate and Adaptive Immunity Mechanisms Explained

Phagocytic Cells

These are defenses found after the first line. Some of these responses are nonspecific; that is, they attack a variety of microbes. One type of response involves cells with phagocytic capacity. Among these are macrophages, neutrophils, and NK cells.

Plasma Proteins

The last barrier participating in the processes of natural immunity involves specific proteins called cytokines, interleukins, or lymphokines. These are involved in inducing the response of white blood cell production.

Other proteins in the blood involved in the innate defense of the organism include:

• Interferons: Proteins released by cells in the body that have been infected by viruses.
• Complement System Proteins: Consists of twenty plasma proteins that bind to membranes and are normally inactive. When activated, complement enhances certain immune, allergic, and inflammatory reactions, which help defend the body. Complement activation may occur through an immune response or invading microorganisms. When activation occurs, large protein complexes called the membrane attack complex are formed.

Adaptive or Acquired Immunity

The main features of adaptive immunity are its specificity and the ability to remember and respond to repeated exposures to the same microbe (memory). It is also known as specific immunity. The components of adaptive immunity are lymphocytes (involved in responses induced by foreign agents) and their products.

Lymphocyte B and T Helper

• B Lymphocytes produce antibodies (proteins that recognize and destroy antigens).
• T Helper cells secrete cytokines that stimulate the proliferation and specialization of other lymphocytes.
• Natural Killer cells are less specialized lymphocytes that destroy infected cells.

Humoral Adaptive Immunity

This results from the production of highly specific proteins generated in response to a particular antigen, called antibodies (corresponding to immunoglobulins). These circulate in the blood and other body fluids. Antibodies also have the ability to neutralize the capacity of infecting pathogens and facilitate their elimination.

Adaptive Cellular Immunity

Intracellular pathogens can survive and proliferate inside phagocytes and other cells where circulating antibodies cannot reach. In this case, the defense against these agents is the responsibility of cellular immunity. It is characterized by the involvement of T lymphocytes.