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 (CD4^bright+) and intermediate CD8 (CD8^dim+) levels and a population of CD8^bright+CD4^dim+ 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.

Glucocorticoids (GC) are highly potent negative regulators of immune and inflammatory responses. Effects of GC are primarily mediated by the glucocorticoid receptor (GR) which is expressed by all cell types of the immune system. It is, therefore, difficult to elucidate how endogenous GC mediate their effects on immune responses that involve multiple cellular interactions between various immune cell subsets. This review focuses on endogenous GC targeting specific cells of the immune system in various animal models of infection and inflammation. Without the timed release of these hormones, animals infected with various microbes or challenged in inflammatory disease models succumb as a consequence of overshooting immune and inflammatory responses. A clearer picture is emerging that endogenous GC thereby act in a cell-specific and disease model-dependent manner, justifying the need to develop techniques that target GC to individual immune cell types for improved clinical application.

Breast cancer (BC) treatment frequently involves microtubule-targeting agents (MTAs), such as paclitaxel, that arrest cells in mitosis. Sensitivity to MTAs is defined by a subset of pro- and anti-apoptotic BCL2 family proteins controlling mitochondrial apoptosis. Here, we aimed to determine their prognostic value in primary tumour samples from 92 BC patients. Our analysis identified high NOXA/PMAIP mRNA expression levels as an independent prognostic marker for improved relapse-free survival (RFS) and overall survival (OS) in multivariate analysis in BC patients, independent of their molecular subtype. Analysis of available TCGA datasets of 1060 BC patients confirmed our results and added a clear predictive value of NOXA mRNA levels for patients who received MTA-based therapy. In this TCGA cohort, 122 patients received MTA-treatment and high NOXA mRNA levels correlated with their progression-free interval (PFI) and OS. Our follow-up analyses in a panel of BC cell lines of different molecular subtypes identified NOXA protein expression as a key determinant of paclitaxel sensitivity in triple-negative breast cancer (TNBC) cells. Moreover, we noted highest additive effects between paclitaxel and chemical inhibition of BCLX, but not BCL2 or MCL1, documenting dependence of TNBC cells on BCLX for survival and paclitaxel sensitivity defined by NOXA expression levels.

Regulatory T (Treg) cells play a key role in immune tolerance and homeostasis. They prevent exaggerated immune responses, autoimmunity, and are crucial in graft‐versus‐host responses. On the other hand, their presence in many tumors is associated with a poor prognosis. In aged individuals, Treg populations are modified with a strong bias toward an effector phenotype and a reduced number of naïve Treg cells, but little is known about the functionality of human Treg cells in old age. The low frequency of Treg cells in human peripheral blood is the main limitation to studying them. Therefore, the development of induced Treg (iTreg) cells has become a valuable tool for in vitro research on peripheral Treg cells. Following a gold‐standard protocol to generate iTreg in vitro , we aimed to investigate age‐related differences in the generation of iTreg cells. However, we detected some unexpected results regarding Foxp3 induction and iTreg functionality. We found no differences in Foxp3 ⁺ CD4 ⁺ generated cells between young and older individuals. Surprisingly, the presence of the cytokine TGF‐β did not play a role in either Foxp3 expression levels or in the suppressive activity of the resulting cells, regardless of the age of the donors. Therefore, we hypothesize that Foxp3 alone does not adequately define bona fide iTreg cells, and the presence of TGF‐β is not essential for the in vitro differentiation of human conventional CD4 ⁺ T cells into suppressive Foxp3 ⁺ cells.