By using blocking antibodies, Peters et al. T cells via the V2 TCR for activation and expansion induces V2+ T cells’ potent killer activity while simultaneously licensing them to suppress T cell responses. Taken together, the study is a further step to understandin more detailthe suppressive activity of V2+ T cells. Electronic supplementary material The online version of this article (10.1007/s00262-019-02469-8) contains supplementary material, which is available to authorized users. showed that up to 30% of V2+ T cells express the Foxp3 transcription factor when they are activated by isopentyl pyrophosphate (IPP) in the presence of IL-15 and TGF-. Foxp3+-enriched V2+ T cells, but not positively freshly isolated V2+ T cells, displayed regulatory/immunosuppressive activity on T cells when co-cultured with autologous PBMCs in the presence of anti-CD3/anti-CD28 mAb [21]. In the study of Peters et al[22] neither IL-2 nor the combination of TGF-1 and IL-15 induced regulatory functions in PAg-expanded T cells on enterotoxin-stimulated CD4+CD25- T cells. On the other hand, T cells initially activated by anti-CD3/anti-CD28 in the presence of TGF- and IL-15 suppressed CD4+CD25- T cells although Foxp3 in T Buflomedil HCl cells was Buflomedil HCl downregulated after transient expression. In contrast to Casettis paper, it was also reported that positively freshly isolated T cells, which are Foxp3-negative, can potently suppress the in vitro proliferation of CD4+ T cells in the presence of anti-CD3/anti-CD28 mAb stimulation in the co-culture [22, 23]. In addition, Traxlmayr et al. [24] demonstrated that in the presence of antigen presenting cells, V2+ T cells stimulated with IPP, but not negatively freshly isolated V2+ T cells, can inhibit the proliferation of CD4+ and CD8+ T cells reacting to strong recall antigens or allo-antigens. Combining these findings, Peters et al[18, 22] suggested that T cells exert their suppressive function only in the presence of anti-CD28 stimulation or antigen-presenting cells and that anti-CD28 stimulation rather than Foxp3 expression correlates closely with the suppressive capacity of T cells. Moreover, as discussed by Weschs group, Foxp3 expression in suppressive human peripheral blood-derived V2+ T cells cannot be detected with the Treg-specific 259D mAb [22] but Buflomedil HCl can be identified with the PCH101 mAb that does not correlate with suppressive function [25, 26]. Clarity on this issue could be derived from methylation studies of the gene [27]. Taken together, it is still controversial as to whether Foxp3 expression is critical, or whether PAg stimulation is sufficient or additional cytokines are necessary for LRP2 V2+ T cells to exhibit cell-contact dependent suppression. In the thymus, differences in signal strength dictate versus lineage choice through modulation of lineage specific transcription factors, while other signaling pathways that integrate with TCR signaling impact the resulting lineage outcome through altering activity of key proteins [28]. In light of this, it seemed Buflomedil HCl likely that in the periphery, graded signals downstream of the TCR may result in differential functional maturation of T cell effector subpopulations while, at the same time, environmental cues such as cytokines might further modulate TCR signaling strength and effector function. The purpose of the present study therefore was to elucidate the role of Buflomedil HCl the TCR in the acquisition of suppressive properties of peripheral human V2+ T cells on autologous T cells, specifically to address whether and how graded.