Respiratory Immunity Flashcards
(36 cards)
what part of the respiratory tract does the mucosal immune system protect
upper respiratory tract
large airways
components of the mucosal immune system
lymphoid nodules - contain DCs, T cells, B cells
generates a LOCAL immune response and recruits activated lymphocytes back to respiratory tract
what part of the respiratory tract does the systemic immune system protect
lower respiratory tract
small airways/lung parenchyma
components of the systemic immune system
does NOT contain lymphoid nodules
relies on immune cells to traffic into the site for immune response
generates an ANTIBODY response (early IgM and late IgG)
components of innate response to viral respiratory infections
NK cells
neutrophils
alveolar macrophages
pDCs
DCs
role of NK cells and neutrophils in innate response to viral infection
first responders; generate inflammation and kill virus
role of alveolar macrophages and pDCs in innate response to viral infection
produce type 1 interferon in response to TLR activation
type 1 IFN inhibits protein synthesis in virally infected cells
role of DCs in innate response to viral infection
activate the adaptive response by migrating to LNs
how does the adaptive immune system respond to viral infection
generates antigen specific CD8 T cells in LN –> returns to site of infection using addressins
addressins
specific cell surface proteins that interact with endothelium to help guide antigen specific T cells to return to the correct site
MALT
mucosa associated lymphoid tissue
specialized organized lymphoid tissue (tonsils + lymphoid follicles) containing DCs, T and B cells
constantly samples antigen from the airways
M cells
specialized microfilm cells that lack microvilli and mucus layer
overlies the MALT to constantly sample antigen from respiratory lining fluid and transfer it to the basal membrane via transcytosis –> delivers it to underlying DCs and lymphocytes –> initiates adaptive immune response
IgA
predominant antibody present in mucosal surfaces
neutralizing - prevents virus from infecting host cells
how are IgA plasma cells formed and where do they go
produced after class switch
localized and maintains lymphoid tissue of respiratory tract
how does IgA get secreted onto mucosal surfaces
- IgA binds polymeric Ig receptor located on basolateral surface of epithelial cell
- gets transcytosed across the cell
- gets secreted into the airway lumen on the apical side of the epithelial cell; remains bound to secretory component of polymeric Ig receptor
secretory pIgR
bound remainder of the pIgR that binds mucins in the mucus layer of the respiratory tract and protects IgA from proteolytic cleavage
mucociliary escalator
ciliated epithelial cells beat in coordination in order to push pathogens from the deep lung up the trachea and out through the nasal opening
important protective factor of the respiratory tract
what does loss of mucociliary escalator cause
increased risk of bacterial pneumonia
ex. bordetella causes ciliary stasis
how can host protect itself against bordetella
produce SP-A (surfactant protein A) which blocks bord from binding to ciliated epithelium
mucin layer
production of mucins by goblet cells creates a mucus layer on top of epithelium that protects host cells from pathogens
needs to be thick enough to be protective but serous enough to allow cilia to move
how does the respiratory epithelium actively participate in the immune response
- TLRs/NOD-like receptors activate the NFkB pathway
- produces AMPs and chemokine to recruit neutrophils, inactive macrophages, and DCs
- produces cytokines (IL-1 and 6) that activate macrophages
NFkB pathway
generates a pro-inflammatory response by epithelial cells
alveolar macrophages
primary cellular protection of the lower respiratory tract
- detects small (<5 um) particles that deposit in the lower respiratory tract
resident cells (do NOT leave the alveolus)
what is the predominant Ig in alveolar fluid lining
IgG
