Nonspecific Host Defenses Introduction Skin & Mucous Membranes Phagocytosis Inflammation Fever Antimicrobial Substances

Defenses - Introduction l Ability to ward off disease is resistance l Lack of resistance is susceptibility l Resistance is of two types –Nonspecific – body defenses that ward off disease without respect to organism –Specific – attack a specific type of organism; usually associated with immune system

Defenses – Skin & Mucus l Physical Factors –Intact skin & keritin resist microbes –Lacrimal apparatus (tears & blinking protect eyes –Saliva washes teeth & gums –Mucus traps microorganisms & ciliary escalator moves mucus up & out –Urine and vaginal secretions keep organisms out of genitourinary tract

Defenses – Skin & Mucus l Chemical Factors –Sebum – unsaturated fats which inhibit microogansisms on skin (some bacteria can metabolize – acne) –Perspiration –washes bacteria – high salt –Lysozyme digest cell wall; found in saliva, nasal secretions, tears and perspiration –Acid (pH 1-3) prevents bacterial growth in stomach –Normal bacteria inhibit pathogens

Defenses - Phagocytocis l Ingestion of microorganisms or particles by a cell - phagocytosis l Usually accomplished by white blood cells

Defenses - Phagocytocis l Blood composition –Fluid (plasma) – water, ions, proteins –Formed elements (cells) »Erythrocytes (red blood cells) »Platlets »Leukocytes (white blood cells) l Granulocytes (neutrophils, basophils, eosinophils) l Lymphocytes l Monocytes

Defenses - Phagocytocis l Actions of Phagocytic cells –Neutrophils & Monocytes –Monocytes are “fixed” or “wandering” –Fixed phagocytes are located in selected tissue, i.e. spleen –Granulocytes predominate in early infection; monocytes are present later in infection –Phagocytes are activated by bacterial components (lipid A) or cytokines (chemical messengers)

Defenses - Inflammation l Inflammation is a bodily response to cell damage l Characterized by –Redness –Pain –Heat –Swelling –Loss of function

Defenses - Inflammation l Inflammatory Response Release of chemical signals –Histamine-a biogenic amine involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Evidence indicates that histamine plays an important role in chemotaxis of white blood cells. Derived from histidine. –Kinins-any of various structurally related polypeptides, such as bradykinin and kallikrein. They act locally to induce vasodilation and contraction of smooth muscles. –Prostaglandins-One of a number of hormone-like substances that participate in a wide range of body functions such as the contraction and relaxation of smooth muscle, the dilation and constriction of blood vessels, control of blood pressure, and modulation of inflammation. Prostaglandins are derived from a chemical called arachidonic acid.

Defenses - Inflammation l Phagocytes move to site of inflammation –Can stick to lining of blood vessels (margination) –Can squeeze through blood vessels (emigration) l Pus is the accumulation of damaged tissue and dead microbes, granulocytes and macrophages

Defenses - Inflammation

Defenses - Fever l Fever is high body temperature (>100.5°F) produced in response to infection l Fever is induced by –Endotoxins –Interleukin-1 (a cytokinin) –LPS endotoxins (exogenous) l Stages –Chill – rising body temperature –Crisis – sweating; falling body temperature

Defenses – Antimicrobials Substances l The Complement System – a system of proteins which inactivate cells l Interferons – antiviral proteins

Defenses - Complement l A group of 8-25 serum proteins that activate one another to destroy cells l Two pathways classical and alternative l Both pathways activate protein C3 of system which binds to cell surface –Opsonization (coating bacteria –promotes phagocytosis) –Cell lysis (through further activation) –Inflammation

Defenses - Complement l Streptococcus especially provokes inflamation l People tend to produce antibodies to cell wall rather than capsule l Peptidoglycan & teichoic acid ellicit production of IL- 1 & TNFa l Opsonization would occur at cell surface but prevented by capsule l Results in escalating inflamatory response because bacteria are not cleared l Fluid accumulates in lungs disrupting gas exchange and essentially suffocating patient

Defenses - Complement

Defenses - Interferons l Antiviral proteins l 3 types alpha, beta & gamma l Produced by virus infected cell and migrate to uninfected cells that then produce antiviral proteins l Host cell specific but not virus specific