innate immune system Flashcards
what are the barriers to infection (first line of defence)
physical - skin, mucous membrane and bronchial cillia
physiological - sneezing, diarrhoea, coughing and vomiting (expel pathogen)
chemical - gastric acid or antimicrobial molecules
biological - flora e.g on skin or in GI tract
what is flora
no harmful pathogens. ONLY harmful when end up in wrong place (UTI). their role is to compete with pathogens for space and produce antimicrobial chemicals
how flora invading other areas can cause clinical problems
skin breached and normal flora enters body e.g during surgery.
fecal oral route- ingestion of feaces contaminated food
fecal perineal-urethral route= UTI
what happens to flora during loss of immune system
flora overgrows e.g in diabetes, AIDS, malignant disease and chemo and when you take antibiotics because it kills good flora which keep bad bacteria at bay. (thrush)
explain the innate immune system
- microbes enter body (first line of defence overcome)
- PAMPS are recognised by PRR’s found on phagocytes and they bind each other
- phagocyte engulfs pathogen and degrades it by phagocytosis. kill pathogen by either oxygen dependant (respiratory burst) or oxygen independent pathway.
what are opsonins
opsonins bind pathogens. phagocytes easily recognise opsonin and bind them and then destroy the pathogen. this helps clear and recognise pathogens more easily
explain phagocytosis
microbe ingested = phagosome. phagosome + lysosome = phagolysosome. microbe is digested by enzymes and then waste is discharged.
what is the complement system
composed of serum proteins which act as enzyme precursors for pathways which result in the activation of 3 pathways. it enhances ability of antibodies and phagocytic cells to clear immune system. also attacks pathogen membrane and causes inflammation
3 types of protein from the complement system
c3a and c5a- recruit phagocytes to site of injury
c3b-c4b- opsonise pathogens
c5-c9- kill pathogens by membrane attack complex
what are the 3 types of complement pathways and how are they activated
classical = complement activation of meoclules bound by anitbodies
lectin = complement pathway activation by molecules bound by MBL
alternate pathway= activates complement by any cell that lacks a complement.
what are cytokines and their functions
cells related by immune cells e.g T and B. cause chemoatraction, phagocyte activation and inflammation
interventions that affect primary defence barriers. (first line of defence)
immune supressor, cathater, antacids, tube in trachea, surgery/open wounds, other diseases e.g CF and antibiotics
types of opsonins
complement protein- c3b - c4b
antibodies - IgG and IgM
acute phase proteins- CRP and MB2
what is CRP
binds to phospholipids on surface of bacteria and acts as opsonin stimulating phagocytosis. CRP levels increased during acute inflammation and a good way of monitoring disease activity and response to treatment
about neutrophils
present in blood. increased during acute infection and recruited by chemotaxis to site of infections. present as pus when they accumulate.
