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Essence of immune response is to recognize foreign substances and to neutralize, eliminate, or metabolize them with or without injury to the body's own tissues.

Functions of the Immune System

1. Defense: protection against antigens. An antigen is a protein or protein complex recognized as nonself.
2. Homeostasis: removal of worn out or damaged components (e.g., dead cells)
3. Surveillance: ability to perceive or destroy mutated cells or nonself cells.

Alterations in Immune Functioning
See Table 4.1

TABLE 4.1 Alterations in Immune Functioning

Types of Immunity
There are two major types of immunity: natural (or innate) and acquired.

1. Natural (innate) immunity: immune responses that exist without prior exposure to an immunologically active substance. Genetically acquired immunity is natural immunity.
2. Acquired immunity
1. Immune responses that develop during the course of a person's lifetime.
2. Acquired immunity may be further classified as naturally or artificially acquired, active or passive. Active immunity results when the body produces its own antibodies in response to an antigen. Passive immunity results when an antibody is transferred artificially.
1. Naturally acquired active immunity: results from having the disease and recovering successfully
2. Naturally acquired passive immunity: antibodies obtained through placenta or breast milk
3. Artificially acquired active immunity: conferred by immunization with an antigen
4. Artificially acquired passive immunity: antibodies transferred from sensitized person (e.g., immune serum globulin [gamma globulin])

Components of Immune Response

1. Located throughout the body
2. Organs include thymus, bone marrow, lymph nodes, spleen, tonsils, appendix, Peyer's patches of small intestine.
3. Main cell types are WBCs (especially lymphocytes, plasma cells, and macrophages); all originate from the same stem cell in bone marrow, then differentiate into separate types.
1. Granulocytes
1. Eosinophils: increase with allergies and parasites
2. Basophils: contain histamine and increase with allergy and anaphylaxis
3. Neutrophils: involved in phagocytosis
2. Monocytes (macrophages) (e.g., histiocytes, Kupffer cells): involved in phagocytosis
3. Lymphocytes (T cells and B cells): involved in cellular and humoral immunity

Classification of Immune Responses


Cellular Immunity

1. Mediated by T cells: persist in tissues for months or years
2. Functions: transplant rejection, delayed hypersensitivity, tuberculin reactions, tumor surveillance/destruction, intracellular infections

Humoral Immunity

1. Mediated by B cells
1. Production of circulating antibodies (gamma globulin)
2. Only survive for days
2. Functions: bacterial phagocytosis, bacterial lysis, virus and toxin neutralization, anaphylaxis, allergic hay fever and asthma