Lecture 20 Flashcards
What is the function of CRP and SAP?
Acute phase proteins (APPs) that bind to bacterial surfaces (phosphocholine), bind to globular heads of C1q and activate classical complement pathway
Which complement pathways are activated by lipopolysaccharides?
Alternative and classical
What do C3a and C5a do?
Bind to receptors on mast cells and activate them
What do activated mast cells do?
Degranulate, releasing large amounts of histamine and bradykinin that enhances blood flow; causes arteriolar vasodilation, venous constriction in some vascular beds, and increased capillary permeability; increased blood flow and local edema are perceived as itchiness and irritation
What is the first cell to release cytokines and chemokines?
Mast cells
What are the potent neutrophil chemoattractants?
C5a, C3a, IL-8/CXCL8
What do immature DCs do during an extracellular bacteria infection?
Engulf and internalize bacteria (Ags) via PRRs (TLRs)
What do activated DCs do during an extracellular bacteria infection?
Migrate to local LNs via lymphatics
What causes the swelling and local hyperemia in LNs?
Lymphocytes become trapped, activated, and proliferate in inflamed LNs
What is responsible for the homing of lymphocytes to LNs?
L-selectin on lymphocytes and PNaD (peripheral lymph node addressin) on HEVs
Infections caused by pathogenic extracellular bacteria have 2 principle mechanisms. What are they?
- Tissue damage is caused by inflammation at the site of infection
- Bacteria produce toxins which have diverse pathologic effects
Define endotoxins and exotoxins
Endotoxins: components of bacterial cell walls
Exotoxins: secreted by bacteria
What is the function of Th17 cells? What effect do genetic defects in Th17 development have?
Promote local inflammation and recruit neutrophils and monocytes at sites of bacterial infection; genetic defects result in increased susceptibility to bacterial and fungal infections, with formation of multiple skin abcesses
Define septic shock and septic shock syndrome?
Septic Shock: severe pathological consequence of disseminated bacterial infection (sepsis) by some gram-negative/positive bacteria
Septic Shock Syndrome: characterized by circulatory collapse and disseminated intravascular coagulation
What is the main function of IL-10?
Major suppressor of macrophage function
Explain bacterial superantigens?
Bind to class II MHC outside the peptide-binding groove and bind to the variable region of different TCR-beta chains, regardless of the peptide specificity; therefore, superantigens can activate a large number of T cells causing polyclonal T cell activation
What is Kawasaki disease?
Acute, multi-system vasculitis of unknown etiology; evidence suggests that it is a superantigen mediated disease
What is the endogenous pathway of antigen presentation?
Proteins from intracellular pathogens are degraded by the proteasome and the resulting peptides are shuttled into the ER by TAP proteins; these peptides are loaded onto MHC class I and then delivered to the cell surface
What is the exogenous pathway of antigen presentation?
Extracellular pathogens are engulfed by phagosomes; inside the phagosome, the pathogen-derived peptides are loaded onto MHC class II molecules, which activate Th cells that stimulate the production of Abs
What is responsible for the detection of beta-glucan?
Dectin-1
What is the major receptor involved in the nonopsonic recognition of fungi?
Macrophage mannose receptor
