Medical Microbiology Chapter 16 - Immunity



Medical Microbiology Chapter 16 - Immunity

I. Natural and Acquired Immunities

A. Immunity - resistance to infection

B. Natural immunity - inherited and permanent

1. skin

2. cellular secretions

3. immune system: phagocytes, T cells, B cells, complement, lysozymes, interferon

B. Methods of acquiring immunity

1. active - person makes antibodies

a. natural - person is ill, makes antibodies against disease, and recovers

b. artificial - person is vaccinated and makes antibodies against disease

2. passive - antibodies given to person from another source; immunity immediate but temporary (3-5 weeks)

a. natural - congenital - from mother to fetus through placenta, colostrum, or breast milk

b. artificial - injection of gamma globulin, antitoxin, or immune serum

C. Immunization

1. increases individual's resistance to specific diseases

2. given by artificial means

a. foreign antigen) injected: toxin, bacteria, viruses, foreign proteins

-dead or weakened (attenuated)

b. antibodies produced

3. antitoxin - weakens or neutralizes effect of toxin

4. immunoglobulin - functions as antibody

-five classes of immunoglobulins: IgG, IgM, IgA, IgD, IgE

-IgG - most plentiful; crosses placenta to unborn fetus

-IgM - largest; agglutination

-IgA - in tears, saliva, colostrum, intestinal secretions

-IgD - works with IgM; on surface of B lymphocytes

-IgE - desensitizes allergic reactions; produces immunity to parasitic infections

II. Autoimmunity

A. Immune system goes haywire

B. Antibodies form against own tissue causing tissue damage

C. Autoimmune disorders

1. Lupus

2. Ulcerative colitis

3. Rheumatoid arthritis

4. Crohns disease

D. Hypersensitivity (allergy)

1. Definition: exaggerated immune response to an antigen that injures or inflames own tissues

2. antigen

a. foreign protein enters body - exogenous

-grass, pollen, dogs, cats, ragweed, penicillin, shellfish, peanuts, bee sting, etc.

b. host's own tissue - endogenous

3. allergen - antigen that triggers hypersensitivity

4. causes increase in IgE antibodies

5. antibodies bind to certain cells causing reaction

-asthma - bind to bronchi and bronchioles

-hay fever - bind to mucous membranes of respiratory tract and eyes

-hives - bind to skin cells

E. Anaphylactic shock

1. antigen-antibody reaction stimulates massive secretion of histamine

2. facial swelling, breathing problems, headache, falling blood pressure, vomiting, stomach cramps

3. injection of either adrenaline or antihistamine

4. lack of treatment or too late can result in death within minutes

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