I need to know if CD8 gamma delta T cells are considered as Tissue resident memory T cells and they produce interferon/granzyme in wild type mice too?
Dear Rekha Garg, as I know, the decision to be gamma/delta T cells is realized before expression of coreceptors, that begins after successful rearrangement of beta chain of TCR and formation of pre-TCR. Decisions to be gamma/delta or alpha/beta T cells are mutually exclusive, because successful rearrangement of beta chain and formation of pre-TCR cease subsequent rearrangements of gamma/delta genes and vice versa. Therefore, normally, gamma/delta T cells should be DN. Too early rearrangement of TCR alpha-chain or transgenic expression of the one can result in gamma/delta like alpha/beta T cells with phenotype similar to IEL and expressing CD103, but I do not know any evidence in literature, which could suggest their relation to resident memory T cells.
Hi Rekha,
As Dmitry pointed out, gd T cells are phenotypically distinct from skin-resident memory CD8 T cells, and are predominantly double negative - however, they can be CD8aa+ like gut IELs. With regards to epidermal gd T cells, because they seed in the epidermis very early in the mouse's life without having been primed by antigen, they can't really be considered memory T cells, although they form part of an epidermal T cell "niche". Thus they are distinct from CD8+ abTCR+ CD103+ tissue-resident memory T cells but they can make IFNg and IL-2 after ConA stimulation.
As indicated by the very helpful replies provided by Dmitry and Ali, gamma delta T cells are not a component of T resident memory as it was originally described. To approach this from an opposite perspective, T resident memory was originally characterized and defined as a result of investigations into alpha-beta CD8+ T cell biology. Although they share a tissue niche, TRM biology is distinct from intraepithelial gamma-delta T cells. These differences extend beyond the restricted TCR repertoire of gamma-delta T cells and their tendency for innate-like behavior, to differences in patterns of trafficking to target tissues as naive vs. effector T cells, type and magnitude of secondary responses, and long-term maintenance within the tissues.
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