Term 1 Flashcards
(994 cards)
Commensal microbes
help defend the first line of defence:
• Secrete antimicrobials (S. epidermidis)
• Alter surface chemistry (Cutibacterium acnes)
induce protective responses that prevent colonization and invasion by pathogens. On the other hand, these bacteria can directly inhibit the growth of respiratory pathogens by producing antimicrobial products/signals and competing for nutrients and adhesion sites.
invasins
Pathogens may overcome these defences by the production of invasins (proteins associated with the penetration of bacteria into mammalian cells),
Hyaluronidase: Dissolves hyaluronic acid which holds connective tissue cells together
Collagenase: Breaks down collagen in muscle
Kinase: Dissolves blood clots
Phospholipases: Break down phospholipids in cell membranes
Hyaluronidase
: Dissolves hyaluronic acid which holds connective tissue cells together
Collagenase
: Breaks down collagen in muscle
Kinase
: Dissolves blood clots
Phospholipases
: Break down phospholipids in cell membranes
mucous membranes
Made up of epithelial layer and underlying connective tissue layer
• Secretes fluid, viscous glycoprotein (mucus)
• Prevents tracts from drying out (barrier)
• Traps potential pathogens
Lysozyme
in perspiration, tears, saliva, nasal secretions and urine destroys bacterial cell walls
IgA
prevents attachment of microbes preventing penetration of mucous membranes
Sebum
Lowers PH of skin inhibiting growth of pathogenic bacteria and fungi
Bacterial IgA proteases
Immunoglobulin A protease degrades IgA, allowing the organism to adhere to mucous membranes
Neutrophils
(polymorphonuclear leukocytes) active in initial stages of infection – enter infected tissues
Basophils
important in inflammation and allergic responses
Eosinophils
mainly act against parasites – numbers increase upon parasitic worm infection/hypersensitivity reactions
Monocytes
only actively phagocytic once they have entered tissues and matured into macrophages
Granules of NK cells release perforins and granzymes
– kills infected cells & releases microbes for destruction by phagocytes; active against tumour cells
Leukocytosis
Increasedtotalno.WBCinmostinfections;especially bacterial infection
• Duringactivestageofinfectionnumbersmight increase 2 – 4-fold
• Meningitis, infectious mononucleosis, pneumococcal pneumonia & gonorrhea
• Alsooccursinautoimmunedisease(RA),leukemia& in drug toxicity
Leukopenia
DecreasedWBCcountfromimpairedWBC production or increased sensitivity of cell membranes to complement
• Salmonellosis,someviralandrickettsialinfections
• Septicemia – extremely severe bacterial infection
• Alsooccursinautoimmunedisease(lupus), lymphoma, radiation therapy, anticancer drugs, antibiotics & diuretics
Leukocidins
cytotoxin that destroys both neutrophilic leukocytes and macrophages.
Humoral
Antibody-mediated response Extracellular fluids B cells Fast response upon detection Act on Extracellular pathogens Antibody-mediated destruction or neutralization MHC class II proteins
Cell Mediated
T cell-mediated response Location of antigen-presenting tissue T cells Slow response Acts on Intracellular pathogens, cancer cells Cell lysis and programmed death MHC class I proteins
Adaptive immune response - evasion
Concealment of antigens from the host:
• Staying inside host cells without displaying antigens (e.g. latent bovine herpesvirus)
• Infecting ‘privileged sites’ (e.g. microbes that colonise the skin, intestinal lumen, CNS, host cell DNA (retroviruses),
etc.)
Antigenic variation
• During the course of infection in a given individual (e.g. gene switching in brucellosis)
• During spread through the host population, e.g:
- ‘antigenic drift’ as influenza spreads through a community
- ‘genetic shift’ in influenza A virus as human and avian virus strains recombine
Immunosuppression:
Direct action on immune cells (e.g. paramyxovirus (cattle plague) on T cells) or release of immunosuppressive molecules
Cause a rapid ‘hit and run’ infection (e.g. rhinoviruses): invade, replicate and be passed on faster than immune system can respond
15
What is another name for humoral immunity?
Antibody mediated immunity
After production in bone marrow, where do B cells mature?
Spleen