Despite presenting a worse prognosis and being associated with highly aggressive tumors, triple-negative breast cancer (TNBC) is characterized by the higher frequency of tumor-infiltrating lymphocytes, which have been implicated in better overall survival and response to therapy. Though recent studies have reported the capacity of B lymphocytes to recognize overly-expressed normal proteins, and tumor-associated antigens, how tumor development potentially modifies B cell response is yet to be elucidated. Our findings reveal distinct effects of 4T1 and E0771 murine tumor development on B cells in secondary lymphoid organs. Notably, we observe a significant expansion of total B cells and plasma cells in the tumor-draining lymph nodes (tDLNs) as early as 7 days after tumor challenge in both murine models, whereas changes in the spleen are less pronounced. Surprisingly, within the tumor microenvironment (TME) of both models, we detect distinct B cell subpopulations, but tumor development does not appear to cause major alterations in their frequency over time. Furthermore, our investigation into B cell regulatory phenotypes highlights that the B10 Breg phenotype remains unaffected in the evaluated tissues. Most importantly, we identified an increase in CD19 + LAG-3 + cells in tDLNs of both murine models. Interestingly, although CD19 + LAG-3 + cells represent a minor subset of total B cells (< 3%) in all evaluated tissues, most of these cells exhibit elevated expression of IgD, suggesting that LAG-3 may serve as an activation marker for B cells. Corroborating with these findings, we detected distinct cell cycle and proliferation genes alongside LAG-3 analyzing scRNA-Seq data from a cohort of TNBC patients. More importantly, our study suggests that the presence of LAG-3 B cells in breast tumors could be associated with a good prognosis, as patients with higher levels of LAG-3 B cell transcripts had a longer progression-free interval (PFI). This novel insight could pave the way for targeted therapies that harness the unique properties of LAG-3 + B cells, potentially offering new avenues for improving patient outcomes in TNBC. Further research is warranted to unravel the mechanistic pathways of these cells and to validate their prognostic value in larger, diverse patient cohorts.
© 2024. The Author(s).

The contribution of self-peptide-MHC signaling in CD4+ T cells to metabolic programming has not been definitively established. In this study, we employed LLO118 and LLO56, two TCRtg CD4+ T cells that recognize the same Listeria epitope. We previously have shown that LLO56 T cells are highly self-reactive and respond poorly in a primary infection, whereas LLO118 cells, which are less self-reactive, respond well during primary infection. We performed metabolic profiling and found that naive LLO118 had a dramatically higher basal respiration rate, a higher maximal respiration rate, and a higher glycolytic rate relative to LLO56. The LLO118 cells also exhibited a greater uptake of 2-NBD-glucose, in vitro and in vivo. We extended the correlation of low self-reactivity (CD5lo) with high basal metabolism using two other CD4+ TCRtg cells with known differences in self-reactivity, AND and Marilyn. We hypothesized that the decreased metabolism resulting from a strong interaction with self was mediated through TCR signaling. We then used an inducible knock-in mouse expressing the Scn5a voltage-gated sodium channel. This channel, when expressed in peripheral T cells, enhanced basal TCR-mediated signaling, resulting in decreased respiration and glycolysis, supporting our hypothesis. Genes and metabolites analysis of LLO118 and LLO56 T cells revealed significant differences in their metabolic pathways, including the glycerol phosphate shuttle. Inhibition of this pathway reverts the metabolic state of the LLO118 cells to be more LLO56 like. Overall, these studies highlight the critical relationship between peripheral TCR-self-pMHC interaction, metabolism, and the immune response to infection.
Copyright © 2020 The Authors.

The clinical benefit of CTLA-4 blockade on T cells is known, yet the impact of its expression on cancer cells remains unaddressed. We define an immunosuppressive role for tumor-expressed CTLA-4 using chronic lymphocytic leukemia (CLL) as a disease model. CLL cells, among other cancer cells, are CTLA-4+ Coculture with activated human T cells induced surface CTLA-4 on primary human CLL B cells. CTLA-4 on CLL-derived human cell lines decreased CD80 expression on cocultured CD80+ cells, with restoration upon CTLA-4 blockade. Coculture of CTLA-4+ CLL cells with CD80-GFP+ cell lines revealed transfer of CD80-GFP into CLL tumor cells, similar to CTLA-4+ T cells able to trans-endocytose CD80. Coculture of T cells with CTLA-4+ CLL cells decreased IL-2 production. Using a human CTLA-4 knock-in mouse lacking FcγR function, antitumor efficacy was observed by blocking murine CTLA-4 on tumor cells in isolation of the T cell effect and Fc-mediated depletion. These data implicate tumor CTLA-4 in cancer cell-mediated immunosuppression in vitro and as having a functional role in tumor cells in vivo.
Copyright © 2019 by The American Association of Immunologists, Inc.

Nuclear receptor peroxisome proliferator-activated receptor γ (PPAR-γ) activation can prevent immunoinflammatory disorders and diabetes. B cells play protective roles during inflammation as well. However, the roles of endogenous PPAR-γ in the regulatory properties of B cells to relieve inflammation remain unknown. Here, we developed B-cell-specific PPAR-γ knockout (B-PPAR-γ-/- ) mice and found that the conditional deletion of PPAR-γ in B cells resulted in exaggerated contact hypersensitivity (CHS). Meanwhile, interferon-γ (IFN-γ) of CD4+ CD8+ T cells was up-regulated in B-PPAR-γ-/- mice in CHS. This showed that the regulatory function of B cells in B-PPAR-γ-/- mice declined in vivo. Whereas splenic CD5+ CD1dhi regulatory B-cell numbers and peripheral regulatory T-cell numbers were not changed in naive B-PPAR-γ-/- mice. Loss of PPAR-γ in B cells also did not affect either CD86 or FasL expression in splenic CD5+ CD1dhi regulatory B cells after activation. Notably, interleukin-10 (IL-10) production in CD5+ CD1dhi regulatory B cells reduced in B-PPAR-γ-deficient mice. In addition, functional IL-10-producing CD5+ CD1dhi regulatory B cells decreased in B-PPAR-γ-/- mice in the CHS model. These findings were in accordance with augmented CHS. The current work indicated the involvement of endogenous PPAR-γ in the regulatory function of B cells by disturbing the expansion of IL-10-positive regulatory B cells.
© 2018 John Wiley & Sons Ltd.

Intricate processes in the thymus and periphery help curb the development and activation of autoreactive T cells. The subtle signals that govern these processes are an area of great interest, but tuning TCR sensitivity for the purpose of affecting T cell behavior remains technically challenging. Previously, our laboratory described the derivation of two TCR-transgenic CD4 T cell mouse lines, LLO56 and LLO118, which recognize the same cognate Listeria epitope with the same affinity. Despite the similarity of the two TCRs, LLO56 cells respond poorly in a primary infection whereas LLO118 cells respond robustly. Phenotypic examination of both lines revealed a substantial difference in their surface of expression of CD5, which serves as a dependable readout of the self-reactivity of a cell. We hypothesized that the increased interaction with self by the CD5-high LLO56 was mediated through TCR signaling, and was involved in the characteristic weak primary response of LLO56 to infection. To explore this issue, we generated an inducible knock-in mouse expressing the self-sensitizing voltage-gated sodium channel Scn5a. Overexpression of Scn5a in peripheral T cells via the CD4-Cre promoter resulted in increased TCR-proximal signaling. Further, Scn5a-expressing LLO118 cells, after transfer into BL6 recipient mice, displayed an impaired response during infection relative to wild-type LLO118 cells. In this way, we were able to demonstrate that tuning of TCR sensitivity to self can be used to alter in vivo immune responses. Overall, these studies highlight the critical relationship between TCR-self-pMHC interaction and an immune response to infection.
Copyright © 2018 by The American Association of Immunologists, Inc.