Post on 20-Jan-2016
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