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Lecture 4

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Dalhousie University
BIOL 1011
Marty Leonard

I. Innate Response 1. External (Barrier) Defences i) Skin and mucous membranes a. the skin - Skin sweat and oil glands leave skin at a PH between 3-5 (slightly acidic) - Creates a barrier b. digestive tract - lysozyme o Tears contain lysozyme o Washes material out of the eye - gastric juice - Digestion tract connects to environment outside which is why it is considered external c. Respiratory tract - Mucus - Ciliated epithelium 2. Internal defenses In case it gets past external defense i) Cell innate defenses a. Phagocytic – in blood, some organs, etc. – destroy pathogens via phagocytosis (engulf pathogen take in phagocytic cell, puts in vacuole and destroys) they have different molecules on surface different than our own cells, helping to detect pathogens (signaling molecules) a. 60-70% of white blood cells are neutrophils b. Macrophages – big eater c. Dendritic – in skin b. Eosinophil – side beside parasite and inject parasite with enzymes that with kill it c. Natural killer cells – destroy via chemicals II. Antimicrobial Proteins a. Lysozyme b. Interferon’s – specialized for dealing with cells infected with viruses (i.e. Colds and flu) secreted by the cell with the infection, to go to nearby healthy cells to stimulate them to produce chemicals to protect them from being infected stopping virus production III. Inflammatory Response a. local - Mast cells near injury release histamines - Macrophages and neutrophils secrete cytokines - More blood is rushed to this spot, bringing clotting elements, antimicrobial proteins and phagocytes (this is why cuts are warm, red and swollen; because more blood and all these things are brought) b. Systemic - Injured or infected cells stimulate release of neutrophils - Macrophages secrete chemicals that may cause a fever - Fevers speed up metabolism and thus the work of phagocytic cells II. Adaptive (Acquired) Immunity Acquired takes longer to work i) Antigens - Foreign molecules e.g. proteins, polysaccharides - Antigens have several regions – epitopes - Epitopes stimulate immune responses o For each epitope there is a pool of lymphocytes o Epitope and the receptor have to have a reaction to get the immune system going ii) Lymphocytes
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