Lecture 21 Flashcards
Remember that secratory IgA is a _____ (how many components in its structure?), and this is the Ab produced by B-cells in _____ Patches of GALT.
Dimer
Peyer’s Patches
Secratory IgA serves to sequester pathogen and toxins. Where can it act relative to the mucosal epithelium?
It can catch pahtogens and toxins that pass through the epithelium, are in vesicles inside the epithelial cells, and on the lumenal side of the epithelial cells (before the pathogen/toxin is taken up). If IgA binds pathogen/toxin during its transport to the lumenal side, it takes the pathogen/toxin with it.
Goblet cells produce different types of mucins, and this ends up creating inner and outter mucosal layers that reside above the epithelium on the lumenal side. How do these layers function?
The inner layer is dense and prevents bacteria from interacting with the epithelium. The outer layer is less dense, and acts as a food source for comensal bacteria.
The lamina ______ is a thin layer of connective tissue that lies just beneath the epithelium. Together, these two compartments constitute the mucosa. In which of these compartments are the majority of mucosal immune cells? Keep in mind intraepithelial lymphocytes (IELs) are phenotypically distinct from other mucosal immune cells; they are very much like CD___ T-cells. IELs are tissue resident and do NOT reenter circulation. Although they express activation markers, they are immunologicaly _____ under steady-state conditions. IELs are the first line of defense for mucosal tissue.
Propria
In the Lamina Propria
CD8+ T-cells
Quiesscent
There are two types of IELs. Conventional IELs act exactly as CD8+ T-cells, and are thus MHC class ____ restricted. Unconventional IELs are NOT MHC restricted. IL-___ is upregulated by epithelial cells and is important for IEL survival and proliferation. At high concentrations of this cytokine, the epithelial cells upregulate MIC-A and B (stress ligands) which bind ____-like receptors on unconventional IELs.
MHC class 1
IL-15
NK-like receptors
Unlike systemic primary T-cell response, mucosal tolerance leads to no _____ (local or systemic?) T-cell effectors (paradoxically)
No local effector T-cells
Continuous sampling of commensal bacteria leads to development of tolerance, mediated locally by which T-cells? Similarly, local DCs constantly produce anti-inflammatory cytokines –> remember what this does in terms of transforming peripheral CD4+ T-cells.
Local T-regs inhibit inflammatory responses. Anti-inflammatory cytokines like TGF-beta and IL-10 can induce the transformation of CD4+ effector T-cells into T-regs.
