Immune System

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Immune: being highly resistant to a disease because of the formation of humoral antibodies or the development of cellular immunity, or both, or as a result of some other mechanism, as interferon activity in viral infections.

Immunity: the condition of being immune; security against a particular disease.

Immunization: inoculation with specific antigen to induce an immune response.

Immune system: consist of specialized cells – lymphocytes and macrophages – and structures,
including lymph nodes, spleen, thymus, bone marrow, tonsils, adenoids, and appendix. Immune
system and blood are closely related, yet different. The blood includes plasma and numerous
kinds of blood cells. Their cells share a common origin in the bone marrow, and the immune system uses the bloodstream to transport its components.

The immune system includes organs and tissues in which lymphocytes predominate as well as cells that circulate in peripheral blood. Lymphoid organs includes: lymph nodes and vessels, spleen, tonsils, adenoids, appendix, bone marrow, thymus, and intestinal lymphoid tissue. The bone marrow and thymus play a role in developing the primary cells of the immune system: B cells and T cells.

Immunity: Refers to the body’s capacity to resist invading organisms and toxins. Preventing tissue and organ damage. The immune system’s cells and organs perform that function. The immune system uses three basic defense strategies: protective surface phenomena, general host defenses, and specific immune responses. It is designed to recognize, respond to, and eliminate foreign substances, such as bacteria, fungi, viruses, parasites,, and preserves the internal environment by scavenging dead or damaged cells and by performing surveillance.

Protective surface: Physical, chemical, and mechanical barriers work to prevent organism entry.
Intact and healing skin and mucous membranes provide the first line of defense against microbial invasion, preventing attachment of microorganisms. Skin desquamation and low pH further impede bacterial colonization. Seromucous surfaces, such as the conjunctiva of the eye and the oral mucous membranes, are protected by antibacterial substances, such as the enzyme lysozyme, found in tears, saliva, and nasal secretions.

The respiratory system requires special protection because microorganisms enter it easily from
outside. Nasal hairs and turbulent airflow through the nostrils filter foreign materials. Nasal
secretions contain an immunoglobulin (naturally produced antibody) that discourages microbe
adherence. A mucous layer that’s continuously sloughed off and replaced lines the respiratory
tract. The mucous layer, coupled with ciliary action, traps and expels inhaled particles and
microbes before they can damage delicate alveolar tissues.

The gastrointestinal system, saliva, swallowing, peristalsis, and defecation mechanically remove
bacteria. The low pH of gastric secretions is bactericidal, rendering the stomach virtually free of
viable bacteria. Resident bacteria prevent colonization by other microorganisms, protecting the
remainder of the gastrointestinal system (GI) through a process known as colonization resistance.

The urinary system is sterile except for the distal end of the urethra and the urinary meatus. When functioning together, urine flow, low urine pH, and immunoglobulin, and the bactericidal effects of prostatic fluid (in men) impede bacterial colonization. A series of sphincters also inhibits bacterial migration.

General host defenses: Once an antigen penetrates the skin or mucous membrane, the immune
system launches nonspecific cellular responses in a attempt to identify and remove the invader.
These nonspecific responses differentiate self from nonself but can’t distinguish specific antigens or respond to them differently. Inflammation, the first of these response against an antigen, causes four characteristic signs and symptoms: heat, redness, swelling, and pain. Neutrophils and
macrophages engulf, digest, and dispose of the antigen. Macrophages and lymphocytes move to
the site of insult and infection by two means: diapedesis (blood cell migration from the
intravascular compartment to tissue sites) and chemotaxis (movement toward a chemical attractor).

Specific immune responses: All foreign substances elicit the same response in general host
defenses. By contrast, particular microorganisms or molecules activate specific immune responses
and can initially involve specialized sets of immune cells. It is classified as either humoral or cell
-mediated immunity. Lymphocytes (B cells and T cells) produce the responses.

Humoral Immunity: In this specific response, an invasive antigen causes B cells to divide and
differentiate into Plasma cells that produce and secrete antigen-specific antibodies. There are five
types of antibodies, or immunoglobulins: IgA, IgD, IgE, IgG, and IgM. Each type serves a
particular function: IgA, IgG, and IgM protect against viral and bacterial invasion; IgD acts as an
antigen receptor of B cells; and IgE causes an allergic response.

After the body’s initial exposure to an antigen, a time lag occurs during which little or no antibody
can be detected. During this time, the B cell recognizes the antigen, and the sequence of division, differentiation, and antibody formation begins. This primary antibody response occurs 4 to 10 days after first time antigen exposure, during which immunoglobulin levels increase, then quickly dissipate, and IgM antibodies form.

Subsequent exposure to the same antigen initiates a secondary antibody response. In this
response, memory B cells manufacture antibodies (mainly IgG), achieving peak levels in 1 to 2
days. These elevated levels persist for months and then fall slowly. The secondary immune
response is, therefore, faster, more intense, and more persistent, and it amplifies with each
subsequent exposure to the same antigen.

An antigen-antibody complex forms after the antibody reacts to the antigen. It serves several
functions. First, a macrophage processes the antigen and presents it to antigen-specific B cells.
Then the antibody activates the complement system, causing an enzymatic cascade that destroys
the antigen. The activated complement system bridges humoral and cell-mediated immunity and
results in the arrival of phagocytic neutrophils and macrophages at the antigen site. This
combination of humoral and cell-mediated immune responses is common.

Cell-mediated immunity: protects the body against bacterial, viral, and fungal infections and
resists transplanted cells and tumor cells. In the cell-mediated response, a macrophage processes the antigen, which is then presented to T cells. Some T cells become sensitized and destroy the antigen; others release lymphokines, which activate macrophages that destroy the antigen. Sensitized T cells then travel through the blood and lymphatic systems, providing ongoing surveillance in their quest for specific antigens.

Diagnostic tests: The doctor may order several variation of tests to evaluate the patient’s immune response. Most common test studies include general cellular tests, such as T- and B lymphocyte assays, to aid diagnosis of primary and secondary immunodeficiency diseases; and general humoral test, such as complement assays, to help detect immuno-mediated disease. He may also order a scratch allergy tests and intrademal skin tests, to evaluate the cell-mediated immune response.

Lab studies such as: WBC or white blood cell count, ESR or Erythrocyte sedimentation rate, Platelet count, Direct antiglobullin test, immunoelectrophoresis, and ELISA enzyme-linked

Disorders: Immune disorders may result from hyperreactivity, as in allergic rhinitis; autoimmunity, as in SLE; or immunodeficiency, as in AIDS.

Symptoms: Symptoms varies with each disorder

Fatigue, dyspnea, malaise, frequent or recurrent infections, or slow would healing.

Treatment: Varies (search your disired disorder for info.)