T helper 3 cell

Add links
Source: Wikipedia, the free encyclopedia.

T helper 3 cells (Th3) are a subset of

T cell receptor (TCR) signalling.[3]

The function of

TGF-β and IL-10. TGF-beta promotes the class switch to low concentrations of IgA which is noninflammatory. IgA does not usually activate the complement system and is not involved with phagocytosis
. Th3 inhibits Th1 and Th2 cells.

Th3 cells have different

TGF-β, IL-4, and IL-10
.

Findings suggest that Th3 cells are a different lineage from naturally arising CD25+CD4+ Treg cells, but it is still unclear whether Th3 cells are the same as induced Treg cells because of the lack of a specific marker for Th3 cells. It was previously shown that TGF-β was produced by intestinal

cytotoxic T-lymphocyte antigen 4 (CTLA-4), which is constitutively expressed on naturally arising Treg cells,[7]
it is possible that TGF-β production from Treg cells through CTLA-4− mediated signaling may stimulate the differentiation of both induced Treg cells and Th3 cells.

Th3 phenotype and secreted molecules

Th3 cells arise from naive CD4+ T lymphocytes in the presence of TGF-β, express CD4, CD69, LAP and produce TGF-β. Unlike the well characterised T regulatory cells (Treg), Th3 cells do not express transcription factor FOXP3. Currently there is no specific transcription factor defining Th3 cells. (transforming growth factor β, TGF-β; latency-associated peptide, LAT; T cell receptor, TCR)
T helper 3 cell (Th3 ) phenotype.

Th3 cells are characterised as CD4+CD25−CD69+FOXP3-LAP+ cells. Unlike the well characterised T regulatory (Treg ) cells, Th3 cells do not express transcription factor FOXP3. There is a lack of specific transcription factor for full and reliable recognition of the Th3 cell population.[2]

Type II-lectin receptor CD69 is presented on cell surface shortly after activation. The presence of CD69 is not specific for Th3 cells, since it is expressed on other lymphocytes, mainly subsets that are tissue resident.[8] The latency-associated peptide (LAP) noncovalently bounds TGF-β and can be expressed by many cells of the immune system.[9]

In tumors Th3 cells can express

lymphocyte activation gene-3 (LAG3). Th3 cells produce vast amounts of TGF-β and to a lesser degree also the anti-inflammatory cytokine interleukin 10 (IL-10). In colorectal cancer Th3 cells were described as 50 times more potent immune suppressors than the classical regulatory FOXP3+ T lymphocytes and their functions was mainly mediated by secretion of suppressive cytokines.[10]

LAG3 acts as a negative regulator of T cell activation and function and can also be expressed on NK cells and other T cells, than Th3. Because of its structural similarity to CD4, LAG3 can bind MHC class II molecules.[11]

Activation and effector functions

Th3 cells can be activated by TCR stimulation after the recognition of an antigen or induced from CD4+ T lymphocytes by TGF-β in the presence of IL-10 and IL-4 cytokines.[12]

Th3 participate in the regulation of the immune response via mechanisms independent on cell-to-cell contact. Secretion of anti-inflammatory cytokine TGF-β by Th3 cells helps to maintain homeostasis in the gut and suppress exaggerated inflammatory and autoimmune responses in the body. TGF-β is a crucial cytokine for maintaining the naturally occurring Treg cells, that suppress Th1 and Th2 immune functions.[3]  Th3 cells can also directly suppress Th1 and Th2 cells by secretion of TGF-β and provide help to B cells towards IgA secretion.[1]

References

  1. ^
    PMID 23133752
    .
  2. ^
    PMID 29151021
    .
  3. ^
    PMID 21488901
    .
  4. S2CID 27536160
    .
  5. PMID 15978836
    .
  6. PMID 17378762
    .
  7. PMID 14676299
    .
  8. PMID 28475283
    .
  9. PMID 21426338
    .
  10. PMID 24064667
    .
  11. PMID 28258692
    .
  12. PMID 31134056
    .
Retrieved from "https://en.wikipedia.org/w/index.php?title=T_helper_3_cell&oldid=1184541029"