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Transcript
immunity by : Dr Samia Sadig Moh. Host defence 1 2 Nonspecific Defenses There are several categories of nonspecific defenses: Physical barriers: skin & mucus membranes. Secretions. Phagocytes? Interferons Complement Inflammatory response Fever Normal flora. 3 Skin Most imp barrier. Epidermal epithelium has multiple layers of dead, keratinized cells and a network of desmosomes locking the cells together. Can't be penetrated by most organisms unless there is a ?. pH (< 7.0) of skin secretions inhibits bacterial growth Hair follicles secrete sebum that contains lactic acid and fatty acids both of which inhibit the growth of some pathogenic bacteria and fungi Areas of the skin not covered with hair, such as ? are most susceptible to fungal infections 4 The epithelia linings In the digestive, respiratory, reproductive, and urinary tracts . Coughing, sneezing& vomiting? 5 Secretions The stomach contains a very low pH and proteases that can destroy pathogens. Urine flushes the urinary tract while glandular secretions flush the reproductive tract. Saliva, tears, nasal secretions, and perspiration contain lysozyme which damage or kill bacteria. 6 The innate immune responses Involves : Phagocytic cells (neutrophils, monocytes, and macrophages). Cells that release inflammatory mediators (basophils, mast cells, and eosinophils); Natural killer cells (NK cells). Molecules such as complement proteins, and interferon. 7 Complement A set of proteins circulating in plasma. Synthesized by the liver. Complement can be activated by interacting with sugars on a bacterium's surface or by interacting with an antigenantibody complex. 8 Complement Direct lyses Opsonization 9 Inflammation A localized tissue response to injury that results in: pain, redness, swelling, and heat. The goals of inflammation are: -Prevent additional pathogen entry. -Slow the spread of pathogens away from the area. -Mobilize defenses that can overcome the pathogens - Facilitate permanent repair. 10 Fever Bacterial toxins, antigen-antibody complexes, and interleukin-1 (a chemical released by active macrophages) all act as pyrogens. Pyrogens reset the body's thermostat and cause a rise in temperature. The rise in temperature causes an increase in the body's metabolic rate which allows the WBCs to function with greater efficiency. 11 12 Acquired (Specific) immune response Humoral immunity= B- Lymphocytes: Responds to bacteria, parasites, and any extra cellular organism. Cell mediated immunity= T-Lymphocytes. Responds to viruses, intracellular organism, malignant cells, transplanted tissues. 13 Classification into T & BLymphocytes 14 Acquired immune response 15 Presentation of foreign antigens Macrophages phagocytose an organism partially or completely Present some of the organism antigens on its surface Lymphocytes recognize the presented antigens as foreign and respond to it. 16 Antigen Antigens are macromolecules that elicit an immune response in the body. Antigens can be : -proteins -polysaccharides Rarely: -lipoproteins - glycolipids. 17 Acquired immune response Acquired immunity exhibits several important properties: 1-Specificity. 2- Clonal selection. 3-Memory. 4- Tolerance of self antigens. 18 1-Specificity T cells and B cells respond to the molecular structure of the antigen. The antigen's shape/size will determine which lymphocytes will respond to its presence.. Each T cell and B cell has specific receptors that will bind to one specific antigen, ignoring all others. 19 Clonal selection T and B cells in the human body includes millions of different lymphocyte populations. Each population consists of several thousand cells with receptors in their membranes that differ from those of other lymphocyte populations. Each group of lymphocytes will respond to a different antigen. When antigen exposure occurs, a lymphocyte specific for that antigen will divide, producing more lymphocytes with the same specificity. This division results in the production of an army of cells (known as clones) that will deal with the particular antigen. 20 Memory: 1ry & 2ndry response First contact with a foreign antigen production of memory T and B lymphocytes. If the same antigen is encountered again , memory cells response is faster and stronger. 21 4-Tolerance During their differentiation in the bone marrow (B cells) and thymus (T cells), cells that react to antigens normally present in the body are destroyed. Thus, mature T and B cells will ignore normal self-antigens and attack only foreign non-self antigens. Abnormalities in this process autoimmune diseases : ? 22 Cell Mediated Immunity 23 Cell Mediated Immunity Cytotoxic T-cells are antigen specific NK cells are destroyany abnormal body cells, e.g., tumor cells or cells infected by a virus i.e non specific 24 Humoral Immunity 25 Ag-Antibody reactions 26 27 Active immunization Vaccination A weak or dead organism (antigen) is introduced into the body. The immune system imitates a 1ry response and produces memory cells. If the person is exposed to the real disease , the immune system responds by a 2ndry response which is? 28 Passive immunization The subject is injected with serum containing ready made antibodies formed by another animal exposed to the antigen. Examples : snake’s anti-toxin, anti-rabies, anti-tetanus serum. 29 Allergies Allergies are excessive and inappropriate responses to (typically) harmless antigens, such as the pollen. Examples : bronchial asthma, hay fever. contact dermatitis 30 Auto-immune diseases The immune system usually distinguishes "self" from "non-self". Autoimmune diseases result when the immune system attacks and destroys cells and tissues of the body. Juvenile diabetes, Grave's disease, Multiple sclerosis, Systemic lupus erythematosus, and Rheumatoid arthritis are some of the autoimmune diseases. 31 Thank You 32