IEL
TCR+
TCR-(2subset)
resident to the intestinal epithelium
express
express a homodimer of CD8α
the integrin αEβ7
90% - have TCR
induced
natural
expression
CD44,69,16,122,161
resemling ILC
iCD3
iCD8α
expression
CD2, CD5,
CD28, LFA-1 and Thy1
subsets
CD4
derived from antigen-experienced conventional TCRαβ+ T cells
CD8
largest T cell subset in peripheral lymphoid organs, are also found in the IEL compartment.
SOME
migrate into the intestinal epithelium where they can respond to subsequent antigenic challenges as bona fide effector or tissue-resident memory T cells
TCRαβ+CD4+CD8αα+ IEL
human intestinal epithelium
regulation by microbiota
cytolytic activity-granzyme expression
regulatory function
IL10 production
TCRαβ
+CD4+CD8αα+Foxp3− phenotype
by FOXP3 T reg
TCRαβ+CD8αβ+
70-80% of the total IEL
effector or memory cells
granzyme B, CD69, CD103 and β7 integrin.
lower amounts of TNF-α and IFN-γ.
some express CD8αα
express inhibitory and co-activating NK cell receptors
implicated in ciliac
TCRαβ+ or TCRγδ+ T cells
lack expression of
CD2, CD5, CD28, LFA-1 and Thy1
expression of cytotoxic mediators such as granzyme B, and display a variety of NK cell receptors
TCRαβ+ IEL
TCRαβ+CD8αα+ IEL
heterogeneous population of
cells with diverse MHC class I restriction
develop in cryptopatches
TGF-B play arole in CD8aa expression
influenced homeostasis by microbiota
NOD2
Vit D
enriched with LAG3,TGF-B3,FgL-2
immunity against colitis by IL10
TCRγδ+ IEL
10–15% of all IEL are TCRγδ+ cells
MOST Vγ7 and some express Vγ1 or Vγ4
extrathymic origin
development dependent on BTLN rather food or microbiota
expression
IFN-γ, TNF-α,
TGF-β, IL-10, and IL-13, prothymosin β4, keratinocyte growth factor (KGF), and antimicrobial proteins
migration
homotypic
interactions mediated by the tight-junction protein occludin
express antimicrobial effectors
MYD88 mediated
inhibit activation of other immune cells
resemble ILC1
express NKP44
lineage relationship with NK and ILC1
memory-activated phenotype, produce IFN-γ
in response to IL-12 and IL-15, amplified in IBD
a subset intraepithelial
NKp46−Ly49E+ cells
producing IFN-γ in response to IL-12, IL-15, or IL-18
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requires IL-15,
the transcription factor Notch1, the Cd8α enhancer E8I
the thymus leukemia (TL)antigen,
a non-classical MHC class I molecule expressed by IEC that serves as a highaffinity ligand for CD8 (Box 1). T-bet and other transcription factors such as Id2, Ahr and
RORγt are dispensable for their development
function
production of the cytokines monocyte chemotactic protein-1
(MCP-1), IFN-γ and osteopontin, and cytotoxic and phagocytic activities
Alfa4 beta 7, CCR9
Rapid response phenotype
CD4 + T cells receive such cues for re-differentiation from external stimuli within the intestinal epithelium, such as TGF-β, retinoic acid, IFN-γ and IL-27