AR Flashcards
What is the mechanism of S.aureus?
→Pore forming toxins
→Acute inflammation
→Superantigen
What is the mechanism of V. choleare?
→Cholera toxin ADP ribosylation of G protein subunits – increase cAMP
What is the mechanism of M. tuberculosis?
→Macrophage activation- granuloma and tissue destruction
What is the mechanism Rickettsia?
→endothelial infection and dysfunction
What is the mechanism of N. meningitidis?
→Acute inflammation,
→tissue damage
→sepsis due to potent endotoxin
What are the main features of bacterial infection?
→bacterial pathogens live and replicate in extracellular spaces with exceptions
→most acute and dangerous bacterial diseases are caused not by the bacteria themselves but by the toxins they produce
How many bacteria are there in the intestine?
→1014 essential bacteria
What are the mechanical defences in the different parts of the body?
→flow of fluid →perspiration →urine →mucus →tears
What are the chemical defences in different parts of the body?
→sebum(fatty acids, lactic acid, lysozyme)- skin
→enzymes(proteases)
→lysozyme in nasal secretion
→acidic vaginal secretion, spermine and zinc in semen
→lysozyme in tears
What are the microbiological defences in the body?
→normal flora
What are defensins?
→Anti-microbial peptides capable of killing by penetrating microbial membranes thus disrupting their integrity
→active against bacteria, fungi and many enveloped and non-enveloped viruses
What are the types of defensins?
→𝛂-defensins
→β-defensins
What are alpha-defensins secreted by?
→mainly by neutrophils
→Paneth cells
What are Paneth cells?
→highly specialized secretory epithelial cells located in the small intestinal crypts of Lieberkühn
What are beta-defensins secreted by?
→broad range of epithelial cells
→in the respiratory tract, the skin and the urogenital tract
Describe the classical complement pathway
→triggered by antibody-antigen complexes binding to C1
→forms a C3 convertase
→C4b2a, which splits C3 into two fragments; the large fragment, C3b, can covalently attach to the surface of microbial pathogens
→opsonise them
→C3a, activates mast cells, causing the release of vasoactive mediators such as histamine
Describe the alternative pathway
→factors, B, D, H & I, interact with each other, and with C3b, to form a C3 convertase
→activates more C3
Describe the lectin pathway
→mannose-binding lectin (MBL) to mannose residues on the pathogen surface
→activates the MBL-associated serine proteases
→activate C4 and C2, to form the C3 convertase, C4b2a
What are the outcomes of C3 and C5 convertases?
→inflammation- recruitment of C5a and C3a
→lysis- C3b bind to bacteria
→opsonisation
Describe the structure of TLRs
→leucine-rich repeat motifs
→cysteine-rich flanking motif
Which type bacteria is TLR4 found on?
→gram negative, LPS
Which type of bacteria is TLR2 found on?
→gram positive, peptidoglycan
Which types of complement molecules are involved in mast cell degranulation?
→C3a
→C5a
What 3 cells are involved in inflammation?
→monocyte via VCAM on blood vessel
→neutrophil via P-selectin
→lymphocyte via ICAM
How else can neutrophils kill bacteria?
→Neutrophils Extracellular Traps (NETS)
What are the three functions of Abs?
→Neutralise bacterial toxins
→Trigger classical complement pathway by binding of IgM to the bacterial cell surface
→Opsonisation; coating of bacteria with antibody thereby aiding phagocytosis
What does IgM targeting of bacteria initiate?
→classical pathway of complement
→bacterial cell surface is coated in C3b facilitating its phagocytosis
Which Ab is most active in neutralisation?
→IgG
→IgA
Which Ab is most active in opsonisation?
→IgG
Which Ab is most in NK killing?
→IgG
Which Ab is most in mast cell sensitisation?
→IgE
Which Abs are most active in activation of complement?
→IgM
→IgG
Which Ab can cross the epithelium?
→IgA
Which Ab can cross the placenta?
→IgG
Which Ab can diffuse into extravascular spaces?
→IgG
→IgA
Where do dendritic cells present to T-antigen cells?
→secondary lymphoid organs
Example of pathogen that can survive inside macrophages
→Micobacterium tuberculosis
Which cytokine can activate NK cells?
→IL-12
→produced from macrophages
