MHC class II-dependent T-T interactions create a diverse, functional and immunoregulatory reaction circle.
Unlike conventional T cells, innate-like T cells such as natural killer (NK) T cells are selected by homotypic T-cell interactions. Recently, a few reports have shown that T-T CD4(+) T cells can be generated in a similar manner to that for NKT cells. These two types of cells share common functional properties such as rapid response to antigenic encounters and the potential for a panoply of cytokine secretion. However, T-T CD4(+) T cells differ from NKT cells in that they are restricted by highly polymorphic major histocompatibility complex (MHC) II molecules and have a diverse T-cell receptor repertoire. Additional example of T-T interactions was recently reported in which peripheral T cells re-circulate to the thymus and participate in the thymocyte selection process. In this review, we dissect the cellular mechanisms underlying the production of T-T CD4(+) and NKT cells, with particular emphasis on the differences between these two T-cell prototypes. Finally, we propose that T-T CD4(+) T cells serve two major functions: one as an acute-phase reactant against viral infection and the other is the generation of anti-ergotypic CD4(+) T cells for regulatory purposes. All of these features make it possible to create a diverse set of functional cells through MHC class II-restricted T-T interactions.
Lee
You Jeong
YJ
Department of Pathology, Seoul National University, College of Medicine, Seoul, Korea.
Jung
Kyeong Cheon
KC
Park
Seong Hoe
SH
D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002450:Cell Communication / Q000276:immunology*; D017637:Clonal Deletion; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006801:Humans; D055611:Natural Killer T-Cells / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology*; D014157:Transcription Factors / Q000276:immunology
D000949:Histocompatibility Antigens Class II; D014157:Transcription Factors