Nonspecific Host DefensesNonspecific Host Defenses

IntroductionSkin & Mucous Membranes

PhagocytosisInflammation

FeverAntimicrobial Substances

Defenses - IntroductionDefenses - 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 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 & MucusDefenses – 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 - PhagocytocisDefenses - Phagocytocis

Ingestion of microorganisms or particles by a cell - phagocytosis

Usually accomplished by white blood cells

Defenses - PhagocytocisDefenses - 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 - PhagocytocisDefenses - 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 - InflammationDefenses - Inflammation

Inflammation is a bodily response to cell damage

Characterized by– Redness– Pain– Heat– Swelling– Loss of function

Defenses - InflammationDefenses - Inflammation 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 - InflammationDefenses - 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 - InflammationDefenses - Inflammation

Defenses - FeverDefenses - 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)

Stages– Chill – rising body temperature– Crisis – sweating; falling body temperature

Defenses – Antimicrobials Defenses – Antimicrobials SubstancesSubstances The Complement System – a

system of proteins which inactivate cells

Interferons – antiviral proteins

Defenses - ComplementDefenses - 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 - ComplementDefenses - 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 - ComplementDefenses - Complement

Defenses - ComplementDefenses - Complement

Defenses - ComplementDefenses - Complement

Defenses - InterferonsDefenses - 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