Table 6 Innate-like T cell subsets

MAIT cell (mucosal- associated invariant T cell)

CD3⁺, MR1-5OPRU tetramer⁺

In blood, CD3⁺, CD161⁺ and Vα7.2⁺ may suffice

CD3⁺, TCRβ⁺, MR1-5OPRU tetramer⁺

T cells with an invariant TCRα chain paired with a TCRβ chain from a restricted repertoire

The invariant TCRs recognize microbial riboflavin-derivative antigens presented by the non-polymorphic MHC class I-like protein MR1

Invariant natural killer T (iNKT) cell

CD3⁺, CD1d-aGalCer tetramer⁺

In blood, CD3⁺ and Vα24J18 (6B11)⁺ or Vα24⁺/Vβ11⁺ may suffice

CD3⁺, TCRβ⁺, CD1d-aGalCer tetramer⁺

A subset of NKT cells with a limited TCR repertoire

They recognize self and non-self lipid antigens in the context of CD1d

γδ T cells

γδ TCR⁺

γδ TCR⁺

A lineage of lymphocytes defined by the expression of the TCRγδ antigen receptor

Human blood γδ T cells

Most express Vγ9Vδ2 TCR, CD161⁺, NKG2A⁺, CCR5⁺ (and CD16⁺ after activation)

Others are termed Vδ2⁻ but are primarily Vδ1⁺ and are generally TIGIT⁺, CD31⁺, CD127⁺, CD62L⁺, CD49a⁻, CD101⁻ and NKG2D⁺

Naive Vδ2⁻ cells are CD27⁺, CD45RA

Antigen-experienced effector cells are CD27⁻, CD45RA⁺, CXCR3^low and IL-7R⁻

ND

ND

Human intestinal γδ T cells

Most are Vδ2⁻ and Vδ1⁺, mainly CD103⁺, CD38⁺, CD69⁺, CD101⁺, TIGIT⁺, CD5⁻ and CD18⁻

Of these cells, Vγ4⁺ cells uniquely selected on BTNL3–BTNL8 marked by NKp46⁺ and FcεR1γ⁺, whereas Vγ2⁺ or Vγ3⁺ cells are NKp46⁻, FcεR1γ⁻ and CD31⁺

ND

It has been proposed that these intestinal Vδ1⁺ cells be split by effector molecules into a cytolytic subset and an amphiregulin-expressing wound repair subset

Human skin γδ T cells

Mostly Vδ1⁺, NKG2D⁺, CD69⁺, CXCR4⁺, CD44⁺, CD28⁻

ND

ND

Mouse spleen and lymph node γδ T cells

ND

γδ^IFNγ cells: mainly make IFNγ

CD27⁺, CD44⁺, CD45RB⁺, SCART1/2⁻ and CCR6⁻

Mostly TCRVγ1⁺

γδ¹⁷ cells: mainly make IL-17A

CD44^hi, CD27⁻, CD45RB⁻, SCART1/SCART2⁺ and CCR6⁺

They are mostly TCRVγ4⁺

γδNKT cells: a minor subset, make IL-4

NK1.1⁺, PLZF⁺

Mostly express Vγ1Vδ6.3 or Vγ1Vδ6.4

Classified into three main types based on effector potential

Mouse epidermis γδ T cells

ND

Mainly Vγ5Vδ1⁺

CD45RB^hi, CD3^hi and CD103⁺

Mostly dendritic epidermal T cells (DETC) expressing a canonical Vγ5Vδ1 TCR

Mouse dermis γδ T cells

ND

Mainly Vγ6Vδ1⁺ (with some Vγ4⁺ cells)

CD44⁺, CD69⁺, CD103⁺, CCR6⁺, CD27⁻

ND

Mouse uterus γδ T cells

ND

Mainly Vγ6Vδ1⁺ (with some Vγ4⁺ cells)

CD44⁺, CD69⁺, CD3^hi, PD-1⁺, CD27⁻, CD45RB⁻, CD103⁺, CCR6⁺

ND

Mouse intestinal intraepithelial lymphocyte (IEL) γδ T cells

ND

Mainly Vγ7⁺

TIGIT⁺, CD69⁺, CD122⁺, LAG3⁺, Thy1⁻, CD8αα⁺ (about 85%), Fcεr1γ⁺, CD3^hi CD5^low, CD45RB⁺

ND

CD8αα⁺ TCRαβ T cells

most CD8αα+TCRαβ T cells are HLA-DR^hi

Thymic leukaemia (TL) antigen tetramer⁺ and CD8β⁻

Express a CD8αα homodimer instead of the more conventional CD8αβ heterodimer

Double-negative (DN) T cells

TCR⁺, CD3⁺, CD4⁻, CD8αβ⁻, CD56⁻

TCR⁺, CD3⁺, CD4⁻, CD8αβ⁻, NK1.1⁻

Lack the conventional co-receptors CD8αβ and CD4 but do express either TCRαβ or TCRγδ

Extrathymic double-positive (DP) T cells

TCR⁺, CD3⁺, CD4⁺, CD8 (CD8αα or CD8αβ)⁺

TCR⁺, CD3⁺, CD4⁺, CD8 (αα or αβ)⁺

Outside the thymus, DP T cells are a heterogenous population of cells that maintain expression of both conventional T cell co-receptors CD4 and CD8 (either CD8αα or CD8αβ)