Thymic mimetic cells
Thymic mimetic cells are a heterogeneous population of cells located in the
History
Some subsets of these cells were observed as early as the mid-1800s because of their distinct, seemingly misplaced, phenotype. The most readily observed subsets were those accumulating and forming microscopic structures, most notably
Diversity
Although thymic mimetic cells exhibit transcriptional programmes of cells from other tissues, they are not identical to them and share a part of their gene expression with mTECs from which they arise. The entire range of phenotypes as well as the pathways that lead to them are still in need of further research. A recent review recognizes (based on expression of lineage specific transcription factors and cell products) the following subtypes: Basal (skin/lung) mTEC, Enterocyte/hepatocyte mTEC, Ciliated mTEC, Ionocyte mTEC, Keratinocyte mTEC, Microfold mTEC, Muscle mTEC, Neuroendocrine mTEC, Parathyroid mTEC, Secretory mTEC, Thyroid mTEC, Tuft mTEC.[1][2]
Function
Since its discovery in 2001,
The expression of peripheral antigens in mimetic cells strongly implies a function in establishing central immune tolerance. This has been reported[7] but further studies are needed. It is unknown what prompts the mTECs to differentiate into mimetic cells, the lineage specific transcription factors could be induced by AIRE or perhaps other signals. Lineage specific transcription factors expressed by some mimetic cell subtypes have been associated with autoimmune disorders.[1][8][9][10][11]
In addition, some mimetic cells can shape the environment and function of the thymus by producing cytokines.[12][13]