NONSPECIFIC HOST DEFENSES Innate (nonspecific immunity) Defenses present at birth

Innate immunity Characteristics –Present at birth –Always present and available to provide rapid responses to disease –Does not involve specific recognition of a microbe –Acts on all microbes in the same way –No memory response

Nonspecific resistance First line defense –Intact skin –Mucous membranes and secretions –Normal flora Second line defense –White blood cells –Inflammation –Fever –Antimicrobial substances

Skin

Intact skin prevents microbes from entering the skin Break in the skin can allow microbes to enter and cause disease Loss of this barrier protection can lead to serious infection

Mucous Membranes Barrier protection Not as strong as the skin Lining of the respiratory tract, GI tract and genitourinary tract Mucous secretion keeps surfaces moist

Epithelial lining of the trachea

Lacrimal apparatus

Protection for the eye Tears are produced by the lacrimal gland Tears and their washing action helps keep the surface of the eye free from bacterial accumulation LYSOZYME is also found in tears and this enzyme has anti-bacterial action as well

White Blood Cells Granulocytes –Neutrophils –Eosinophils –Basophils Agranulocytes –Monocytes –Macrophages –Lymphocytes

White Blood Cells

WBC numbers Never – neutrophils60-70% Let – lymphocytes 20-25% Monkeys – monocytes3-8% Eat – eosinophils 2-4% Bananas - basophils.5-1%

Phagocytosis (cell eating) Phagocytic WBC’s NeutrophilEosinophilMacrophage

Basophil.5-1% of white cells Not a phagocytic cell Release histamine Inflammation reaction

Lymphocytes T cells and B cells Antibody production and cell-mediated immunity

Phagocytosis

Stages of phagocytosis Ingestion Formation of phagosome Formation of phagolysosome Digestion Discharge

Stages of phagocytosis

Inflammation Defensive local response by body to tissue damage Inflammation is characterized by: –Redness –Pain –Heat –Swelling

Fever Systemic response to injury Increase in body temperature as response to infection Shivering with fever is the results of a new higher set point for body temperature Fever is a defense against disease Fever may help to activate body defense mechanisms

Antimicrobial Substances Complement Interferon

Complement Defensive system of over 30 proteins that are made in the liver and circulate in the blood and tissues Activation of complement destroys microbes by lysis, inflammation, and phagocytosis Complement proteins act in a CASCADE, that is, one reaction triggers another

Complement

Interferon Classes of anti-viral proteins First discovered in the mid 1950’s Produced by cells such as lymphocytes, macrophages and fibroblasts AFTER viral stimulation - RNA viruses Interfere with viral multiplication

Interferon Three classes of interferons –Alpha - leukocytes –Beta - fibroblasts –Gamma - lymphocytes (T cells) Produced after viral infection Induces near by cells to produce anti-viral to protect against the virus Currently produced by recombinant DNA technology

Magic Bullet? Interferon has several limitation to its use –Short term effectiveness –Side effects –High concentrations toxic to heart, kidney, liver, bone marrow –Currently used to treat Hepatitis C –Used in Eastern Europe and Russia to treat colds and flu but this is widely accepted elsewhere

Interferon