Table 1.

Summary of properties exhibited by innate-like, MHC-restricted, and mycolipid-specific T cells.

Topic	Innate-like T cells	MHC-restricted T cells	Mycolipid-specific T cells
TCR diversity	Semi-invariant	Highly diverse	Semi-invariant and highly diverse
TCR promiscuity	Yes	No	Yes
Activation requirements	TCR dependent and independent	TCR dependent	TCR dependent?
Memory phenotype	Acquired during development	Acquired after development	Unknown
Thymic selection	Dependent on thymocytes	Dependent on thymic epithelium	Dependent on thymocytes
Functional profiles	Th1, Th17	CD4 (Th1, Th2, Th17) CD8 (CTL)	Th1 and CTL, some Th17

This table compares the major aspects of T cell biology between innate-like T cells, MHC-restricted T cells, and mycolipid-specific T cells. TCR diversity is evaluated by conservation of TCR sequences across genetically unrelated donors. TCR promiscuity is defined as the ability of the same TCR to recognize several chemically unrelated ligands. The activation requirements for T cell subsets are described as the reliance on TCR ligation for T cell activation. As all three T cell subsets have been shown to exhibit T cell memory in some capacity, we summarized the differences between memory phenotype as acquisition during or after T cell development. Thymic selection describes the cells that are involved in the selection of these T cell subsets during development. Lastly, the functional profiles for these subsets are summarized as the major functional profiles that have been described for T cells in each subset.