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

Defenses - Introduction Ability to ward off disease is resistance Lack of resistance is susceptibility 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 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 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 Ingestion of microorganisms or particles by a cell - phagocytosis Usually accomplished by white blood cells

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

Defenses - Phagocytocis 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 - Phagocytosis Granulocytes

Defenses - Inflammation Inflammation is a bodily response to cell damage Characterized by Redness (rubor) Pain (dolar) Heat (calor) Swelling (tumor) Loss of function (functio laesa)

Defenses - Inflammation

Defenses - Inflammation Inflammatory Response Release of chemical signals Histamine Kinins Prostaglandins A biogenic amine. Regulates physiological function in the gut. Acts as a neurotransmitter. Invovled in chemotaxis of white blood cells. Derived from histidine.

Defenses - Inflammation Kinins Any of various structurally related polypeptides Examples as bradykinin and kallikrein (proteases involved in coagulation). Act locally to induce vasodilation and contraction of smooth muscles.

Defenses - Inflammation Prostaglandins- Found in most tissues and organs Autocrine and paracrine lipid mediators that act upon platelets, endothelium, uterine and mast cells. Involved in 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 Phagocytes move to site of inflammation Can stick to lining of blood vessels (margination) Can squeeze through blood vessels (emigration) Pus is the accumulation of damaged tissue and dead microbes, granulocytes and macrophages

Defenses - Inflammation

Defenses - Fever Fever is high body temperature (>100.5°F) produced in response to infection Fever is induced by Endotoxins Interleukin-1 (a cytokinin) LPS endotoxins (exogenous)

Defenses – Fever - Stages Initial chill - In the first stage of fever also known as the invasion period the patient will experience chill, loss of appetite, and headache. Chill occurs, occurs because of the tightening of blood vessels near the skin.

Defenses – Fever - Stages Rising Temperature - The body is hot and flushed, the skin dry, and the pulse and respiration are rapid. The patient will experience thirst and he/she will feel restless. In high fever, delirium and convulsions may occur.

Defenses – Fever - Stages Crisis - In the final stage before returning to normal, the temperature falls, breathing and pulse slow down, and the skin becomes moist. The patient often sweats.

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

Defenses - Complement A group of 8-25 serum proteins that activate one another to destroy cells Two pathways classical and alternative 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 Streptococcus especially provokes inflamation People tend to produce antibodies to cell wall rather than capsule Peptidoglycan & teichoic acid ellicit production of IL-1 & TNFa Opsonization would occur at cell surface but prevented by capsule Results in escalating inflamatory response because bacteria are not cleared Fluid accumulates in lungs disrupting gas exchange and essentially suffocating patient

Defenses - Complement

Defenses - Complement

Defenses - Complement

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