Legend or Truth: Mature CD4+CD8+ Double-Positive T Cells in the Periphery in Health and Disease

Abstract

The expression of CD4 and CD8 co-receptors defines two distinct T cell populations with specialized functions. While CD4+ T cells support and modulate immune responses through different T-helper (Th) and regulatory subtypes, CD8+ T cells eliminate cells that might threaten the organism, for example, virus-infected or tumor cells. However, a paradoxical population of CD4+CD8+ double-positive (DP) T cells challenging this paradigm has been found in the peripheral blood. This subset has been observed in healthy as well as pathological conditions, suggesting unique and well-defined functions. Furthermore, DP T cells express activation markers and exhibit memory-like features, displaying an effector memory (EM) and central memory (CM) phenotype. A subset expressing high CD4 (CD4bright+) and intermediate CD8 (CD8dim+) levels and a population of CD8bright+CD4dim+ T cells have been identified within DP T cells, suggesting that this small subpopulation may be heterogeneous. This review summarizes the current literature on DP T cells in humans in health and diseases. In addition, we point out that strategies to better characterize this minor T cell subset’s role in regulating immune responses are necessary.

BACH2-mediated CD28 and CD40LG axes contribute to pathogenesis and progression of T-cell lymphoblastic leukemia

“…For example, we found relatively high BACH2 levels in DN T cells but low BACH2 levels in DP T cells compared to other normal peripheral T-cell subsets. This finding seems to be in concordance with the physiological roles of BACH2 [ 12 , 13 ], since peripheral DN T cells are essential for maintaining immune homeostasis under healthy conditions and contribute to immune surveillance and defense [ 33 – 35 ], whereas DP T cells in the periphery exhibit memory-like features [ 36 , 37 ]. As such, further efforts are needed to delineate the molecular mechanisms that govern BACH2 transcription or post-transcriptional regulation in normal and malignant T cells, thus elucidating the biological function of BACH2 in scenarios of both health and disease.…”

Living, Heat-Killed Limosilactobacillus mucosae and Its Cell-Free Supernatant Differentially Regulate Colonic Serotonin Receptors and Immune Response in Experimental Colitis

“…The gut immune system plays a key role in this perturbation of homeostasis between commensal bacteria and the function of the gut barrier [ 6 ]. Its response involves the activation of a variety of intestinal immune cells, including neutrophils, macrophages, T cells, B cells, and dendritic cells [ 7 , 8 ]. It has been observed that the pro-inflammatory CD8 + cytotoxic T lymphocytes can induce a relapse of colitis via the production of interferon-γ in mice [ 9 ].…”