Topic 7.1 Non-specific (PDF)

RNB 10102: MICROBIOLOGY & BIOCHEMISTRY TOPIC 7.1: BODY DEFENSE NON SPECIFIC (First and Second line defense) BY: Kogi  Learning Outcomes After completing this session, the student should be able to: describe the no...

RNB 10102: MICROBIOLOGY & BIOCHEMISTRY TOPIC 7.1: BODY DEFENSE NON SPECIFIC (First and Second line defense) BY: Kogi  Learning Outcomes After completing this session, the student should be able to: describe the non-specific defenses against microbial infection discuss the protection in first line defense describe the types and functions of second line defense ❖Phagocytes ❖Natural killer cells ❖Antimicrobial substance ❖Inflammation ❖Fever  Introduction Individuals normally have defenses that protect the body from infection These defense can be categorized as: ❑Innate/Non specific defense – protect the person against all microorganism, regardless of prior exposure ❑Adaptive/Specific defense – are directed against identifiable bacteria, viruses, fungi or other infectious agent  Body defense mechanism 1st line defense - Skin - Mucous membranes Non-specific 2nd line defense defenses -phagocytes -antimicrobial proteins - Natural killer cells -inflammation - fever …body defense mechanism B and T cells Specific defenses (3rd line) Antibodies  1st line defense Consist of - mechanical & chemical protection Mechanical protection Epidermis of skin- provide physical barrier to the entrance of microbes Mucous membranes – inhibit the entrance of many microbes, but not as effective as intact skin Hairs – trap & filter microbes, dust, pollutants in the nose Mucus – trap microbes in respiratory & gastrointestinal tract  1st line defense …mechanical protection Lacrimal apparatus – tear dilute & wash away irritating substances & microbes Saliva – washes microbes on the oral cavity Flow of urine – washes microbes from urethra Defecation and vomiting - expel toxins and microbes from body  … 1st line defense Chemical protection – reduce bacterial growth Sebum – form a protective acidic film over the skin surface that inhibit growth of many microbes Perspiration – flushes microbes from skin area Lysozyme – anti microbial substance in perspiration, tears, saliva, nasal secretions and tissue fluids - enzyme breaks down bacterial cell walls Gastric juice – low pH (1.5-3.0) destroys most bacteria & toxin in stomach Vaginal secretions – slightly acidity inhibit bacterial growth; flush microbes out of vagina Summary of 1st line defenses  2nd line defense Also a non-specific response (i.e. the response is the same for any pathogen) Attack on any microbes that have survived the first line of defense Consists of: – Phagocyte – Natural killer cells – Antimicrobial protein – Inflammation – Fever  Phagocytes It is a large white cells that can swallow and digest microbes and dead or injured body cells- by phagocytosis Phagocytosis - process of ingestion and destruction of microbes or any foreign particulate matter Main type of phagocytes - neutrophils & macrophages Phagocytes will engulf the pathogen and digest it, and killing of the pathogen Whenever, there is an infection in the body, the total count of leucocytes increases  …phagocytes Dead bacteria may accumulate to form pus at the site of injury Types of phagocytes cells: ❖Macrophage ❖Eosinophil ❖Neutrophil ❖Basophil ❖Mast cell ❖Monocytes  …phagocytes …Types of phagocytes cells Macrophages Known as “big eaters” Long lived & mature from monocytes. It will leave the blood stream, enter tissue and develop into macrophages Wondering macrophages – migrate to the tissues in search and destroying microbes and cellular debris Fixed macrophages - permanent resident of specific organ in the body  …phagocytes …Types of phagocytes cells Neutrophils – phagocytize bacteria, short lived. After entering the tissue – lived in few hours only Eosinophils – secrete enzymes to kill parasitic worms Basophils - contain granules of toxic chemicals that can digest foreign microorganisms. These are cells involved in an allergic response Mast cells - contain a variety of inflammatory chemicals including histamine and serotonin. Cause vasodilatation of blood vessels near wound …phagocytes 5 steps in phagocytosis 1.Chemotaxis :The phagocyte recognizes a bacteria as an invader and move towards it 2. Adherence: phagocytic cells attach to the bacteria through the cell-surface receptors. Extends the pseudopods to surround the bacteria  …phagocytes …5 steps in phagocytosis 3. Ingestion: Once in the neutrophil, lysosomes (vesicles containing digestive enzymes) will form and make their way towards the phagosome containing the bacteria 4. Digestion: The lysosomes will fuse with the phagosome. The bacterium is dissolved by lysozyme 5. Killing: The microbe is destroyed & the phagocytic cell dies as well – a normal death of a cell known as apoptosis  …phagocytes …5 steps in phagocytosis 1 CHEMOTAXIS Microbe Phagocyte 2 ADHERENCE 3 INGESTION Pseudopod Lysosome 4 DIGESTION Digested microbe Plasma in phagolysosome membrane Residual body 5 KILLING (indigestible material) Digestive enzymes Phases of phagocytosis  Once phagocytes do their job, they die and their "corpses,“ and damaged tissue, and fluid form pus  Natural Killer Cells NK cells are lymphocytes that lack the membrane molecules that identify T and B cells Able to kill a wide variety of microbes and certain tumour cells  Release perforins that insert into the plasma membrane of a microbe and make the membrane leaky so that cytolysis occurs Present in the lymph nodes, spleen and red bone marrow  Antimicrobial Protein Lymphocyte and macrophage cells that is infected with viruses will produced protein called interferon ❑Interferon induced uninfected neighboring cells to synthesize (create) antiviral proteins that inhibit viral replication (reproduction) A group of 20 proteins present in blood plasma and on cell membranes comprises the complement system – enhance certain immune, allergic, and inflammatory reactions bind Iron-binding proteins –remove iron from the body fluids thereby inhibiting microbial growth Antimicrobial proteins – produce anti-microbial activity and attract dendritic and mast cells  Inflammation It is a defensive response of the body to tissue damage The response are similar to the response to damage caused by burns, radiation, or invasion of bacteria or viruses Cause of inflammation ❖ Microbes – bacteria, virus, protozoa, fungi ❖ Physical agent – heat, cold, mechanical injury, ultraviolet ❖ Chemical agents ✓ organic - microbial toxin & organic poison ✓ Inorganic – acid, alkalis  …inflammation Functions of inflammation Dispose microbes, toxin or foreign material Prevent spreading to other tissue Prepare the site for tissue repair Help restore tissue homeostasis  …inflammation Symptoms Redness Heat Swelling Pain Loss of Function – depend to site of injury Stages of inflammation Vasodilatation and increased permeability of blood vessels Phagocyte migration Tissue repair  Stage of inflammation Vasodilatation Once the tissue injured, chemical mediators are released ❑Type of chemical mediators - histamines, kinins, prostaglandins, leukotrienes, and complement Function of chemical mediators – Stimulate production of other inflammatory mediators – Stimulate nerve endings, causing pain – Alter capillaries -vasodilatation – Attract and stimulate phagocytes  …stage of inflammation …vasodilatation In response to the chemical mediators, vasodilatation of blood vessel occur & lead to increasing blood flow (hyperemia) ❑helps remove microbial toxins & dead cells ❑Provide more oxygen & nutrient ❑Increase temperature (heat) & redness of inflamed area ❑Contributes to swelling & edema  … stage of inflammation Increased vessel permeability Increased permeability allow antibodies & clot-forming chemicals from blood pass out & enter the injured area – lead to edema & pain Edema – due to an increase amount of interstitial fluid that has leaked out of the capillaries Pain – due to injury of neuron, from toxic chemicals released by microbes & from increased pressure of edema  … stage of inflammation …Increased vessel permeability Lead to increase blood supply ❑helps to dilute harmful substances ❑carries nutrients and oxygen - important for wound healing ❑transport leukocytes to the area for phagocytosis ❑removes debris - dead cells, bacteria and exudates or material and cells discharged from blood vessel  … stage of inflammation Phagocytes mobilization Shortly after inflammation process start, phagocytes move to injured area Chemotaxis - chemical attraction of leukocytes, neutrophil & macrophages to an area of inflammation Neutrophils – first to arrive, begin to squeezed through the wall of blood vessels near to injured area – process emigration/diapedesis  … stage of inflammation …Phagocytes mobilization Phagocytes activity is promoted by raised of temperature Monocytes – slower arrival, arrived after a few hours as neutrophil die off rapidly Once in the tissue, they turn to wondering macrophage that engulf damage tissue, worn-out neutrophils, & invading microbes After 24 hours, macrophage become predominant & persist if the situation not resolve – lead to chronic inflammation  … stage of inflammation Tissue repair Pus – form of dead phagocytes and other WBCs, damaged tissue & microbes If too numerous for effective removal by phagocytes, an abscess may develop Pus may reaches the surface of the body or drain into internal cavity & dispersed or it will remains &gradually destroyed over a period of days & absorbed Summary of Inflammatory Response  Fever Caused by infection from bacteria (and their toxins) and viruses Increases body’s metabolic rate, which speeds up immune defenses and tissue repair Increased need for oxygen & nutrients Increases effects of antimicrobial substances produced by the immune system  …fever Positive effect The high body temperature inhibits some microbial growth and speeds up body reactions that aid repair Promoting the activity of phagocytes Stimulates liver and spleen to sequester iron and zinc (needed by microorganisms) Summary of 2nd line defense Although the second line of defense is very powerful, it does have a some weaknesses: It can’t deal completely with any one particular micro-organism (some pathogens will nearly always survive this attack) It cannot remember past infections. This is why a third line of defense is needed