Lecture 1 Immunology_Dr Momen PDF

General Microbiology & Immunology 1  Microbiology Science studies tiny organisms not seen by naked eyes (microbes or micro-organisms) Microbes: bacteria, viruses, fungi..... * Items to be covered: - General description & classif...

General Microbiology & Immunology 1  Microbiology Science studies tiny organisms not seen by naked eyes (microbes or micro-organisms) Microbes: bacteria, viruses, fungi..... * Items to be covered: - General description & classification of M.Os - Growth, metabolism & cultivation of M.Os - Microbial genetics 3  Components of Immune System 2 Classes: 1- Natural Immunity (Innate immunity): - Inducible - Displays neither specificity (Non-specific) nor memory - Displays self-nonself discrimination 2- Acquired Immunity (Adaptive immunity): - Inducible - Displays specificity (Specific ) & memory - Displays self-nonself discrimination 4 - Present only in vertebrates  1- Natural immunity (Non-specific or Innate immune system) 1- Skin & mucous membranes: a- Intact skin is inaccessible to m.o b- Fatty acids & lactic acids in sweat & sebaceous secretions inhibit m.os c- Mucus trap m.os & foreign particles removed by ciliary action (coughing & sneezing) 2- Body secretions: Contain bactericidal substances: a- Lysozyme in tears, saliva & nasal secretions b- HCl in stomach c- Basic polypeptides as spermine in semen 3- Complement system: Heat-labile serum proteins produced by liver associated with destruction of bacteria 5 4- Interferons: - Proteins produced by leucocytes that Interfere with viral replication - Types: 1- Type I IFN: i- IFN-α: produced by mononuclear phagocytes ii- IFN-β: Produced by fibroblasts 2- Type II IFN or IFN-γ: produced by T-cells 5- Fever (Elevated body temperature): - The thermoregulatory centre in hypothalamus regulates body temp. & affected by: 1- Endotoxins (LPS) of G-ve bacteria 2- Interleukin-1 (IL-1): secreted by monocytes & macrophages Influences of elevated body temp.: a- Enhances Ab production & T-cell proliferation b- Restricts virus replication c- Inactivates microbial toxins 6  7 6- Species-specific Host-parasite relationships: Spp-specific receptors for m.os on cells play role in infection e.g. Smallpox is specific human pathogen & Man NOT susceptible to many animal m.os 7- Acute phase proteins: - Synthesized in liver in response to cytokines (IL-1, IL-6 & TNF-α) - Increase in inflammation (e.g. CRP) - Function: Enhance host resistance & minimize tissue injury 8- Inflammation: - Redness & swelling increase at infection site - Destroy invaders & involved in tissues healing - Many mediators (e.g: histamine) responsible for inflammatory response: - Vasodilatation of capillaries -------> redness of tissues & increased temp. - Increased capillary permeability -------> influx of fluids & cells --> edema - Influx of phagocytes -------> engulf bacteria & release lytic enzymes 9- Normal bacterial flora: - Present at portal of entry - Suppress growth of m.os (by competition for nutrients or production of inhibitors e.g. colicins) - e.g: Vaginal acidic pH maintained by normal flora interfere with pathogens - N.B: Suppression of normal flora by ABs ------> super infection with potential pathogens. 10- Phagocytosis: - By phagocytes (engulfment & digestion of m.os.) - Major line of defense against microbes 8  Mechanism of phagocytosis A- Chemotaxis, Migration & Attachment: - Macrophages attracted to inflammation site by chemotactic substances (e.g. IL-8) - Macrophages ----> cytokines ----> migration of leucocytes & monocytes. - Phagocytes attach to m.os by surface receptors B- Ingestion: - Phagocytes engulf m.os into phagosome - Lysosomal granules fused with phagosome ---> phagolysosome ---> digestion of m.os C- Intracellular killing or digestion: - Oxygen-independent killing: by lysozyme, lactoferrin, hydrolytic & proteolytic enzymes - Oxygen-dependent killing : by superoxide anion, H2O2, hydroxyl radicals 9  Cells involved in immunity Blood cells originate from Hematopoietic stem cells (Pluripotent stem cells) in bone marrow. A- One pathway of differentiation: (Myeloid differentiation) Gives myeloid stem cells ------> differentiate into: 1- Erythroblast ----> Erythrocytes 2- Megakaryocytes ----> Platelets 3- Myeloblast ----> Granulocytes (Basophil, Eosinophil & Neutrophil) 4- Monoblast ----> Agranulocytes (Monocytes) B- Other pathway of differentiation: (Lymphocytic differentiation) Gives Lymphoid stem cells ----> Lymphoblast --> differentiate into: 1- B-lymphocytes (In bone marrow) 2- T-lymphocytes (In thymus) 3- Natural killer cells (NK) 10 Haematopoiesis 11  Types & Function of immune cells Cell type General function - T cells Help, suppression, cytotoxicity, delayed hypersensitivity, memory - B cells Ab production, memory - NK (natural killer) killing - Monocytes Phagocytosis, monokines, Ag processing & Presentation - Neutrophils Phagocytosis-killing - Eosinophils Antiparasitic - Basophils Immediate hypersensitivity, Antiparasitic - Platelets Clotting - Erythrocytes Oxygen & CO2 transport 12  13 Lymphatic organs * Def: Organs where lymphocyte maturation, differentiation & proliferation occurs. * 2 Types: A- 1ry lymphoid organs Where: maturation of T- & B-lymphocytes into Ag recognizing lymphocytes T & B cells acquire their Ag-specific receptors 1- Thymus gland: Lymphoid stem cells differentiate ------> T-lymphocytes Maturation ------> ability to recognize & respond to Ag Recognition ------> by specific receptor on T-cell 2- Bone marrow & Bursa of fabricius: B-cells mature in bursa in birds (in bone marrow in mammals) N.B: Mature B- & T- cells transported to 2ry lymphoid organs (encounter & respond to Ags.)  B- 2ry lymphoid organs 14 Where Ag-driven proliferation occurs (lymphocytes ---> further division & differentiation) Include: Spleen, Lymph nodes, Tonsil, Appendix & MALT (Mucosa-Associated Lymphoid Tissue) e.g. Peyer’s patches (clusters of lymphocytes in small intestine lining) Function: 1- Trapping foreign substances 2- Main sites of production of Abs & generation of Ag-specific T-lymphocytes * Spleen. **Lymph nodes. Thanks 15