Biology subjects

Kuhns, M. S.

Publications and source records attributed to Kuhns, M. S..

7 recordsLinked to original sources

bioRxiv2025

Impact of Absent in Melanoma 2 (AIM2) on Antigen-Specific CD4+ T cell Activation and Homeostasis.

The intrinsic role of Absent in Melanoma 2 (AIM2) in CD4+ T cells during antigen-specific activation and differentiation is not fully understood. To address this, we crossed AIM2-deficient mice with OT-II/RAG transgenic mice, which express an ovalbumin-specific T cell receptor in CD4+ T cells (OT-II). We found that AIM2 does not regulate thymic selection of CD4+ thymocytes, but may promote trafficking or survivability of CD4+ T cells in the spleen. In vitro coculture assays revealed that Aim2-/- OT-II CD4+ T cells produce significantly less IL-2 than wild type OT-II CD4+ T cells when cocultured with ovalbumin-incubated dendritic cells. However, we found no differences in CD4+ T cell proliferative capacity and differentiation among WT OT-II and Aim2-/- OT-II CD4+ T cells following OVA immunization in vivo. Finally, adoptively transferred WT and Aim2-/- OT-II cells controlled the growth of implanted OVA-expressing NOOC2 syngeneic tumors at an equal capacity. Taken together, these results indicate that AIM2 contributes to CD4+ T cell homeostasis in secondary lymphoid organs in vivo. AIM2 also intrinsically promotes IL-2 production in response to antigen-specific activation in vitro. However, this loss of IL-2 does not translate to measurable defects in proliferative, differentiation or effector function during OVA immunization or tumor challenge in vivo.

immunology↗

bioRxiv2025

Discovery Stack Pilot: Feasibility and Outcomes of a Scientist-Designed Peer Review Model Separating Quality and Impact

Peer review serves as the cornerstone of scientific quality control. Yet, the current journal-centric system is hindered by long timelines, high publication costs, inconsistent review quality, systemic biases, and editorial gatekeeping. Notably, the system relies on misaligned measures of impact that are tethered to journal branding and conflate scientific rigor (Quality) with perceived significance (Impact). Here, we report findings from the Discovery Stack Pilot Study, which tested a scientist-designed, journal-independent peer review model. The Discovery Stack model integrates in-line reviewer comments to promote constructive feedback and separately evaluates scientific Quality and Impact using defined criteria. To examine feasibility and effectiveness, manuscripts were reviewed in parallel with traditional journal review. A total of 162 reviews were completed, and survey data from 86 participants were analyzed. The results showed that reviewers effectively evaluated Quality and Impact as separate dimensions, with Quality scores being more consistent across reviewers than Impact scores. Participants strongly supported the core elements of the Discovery Stack model and expressed enthusiasm for its broader adoption to enhance transparency, efficiency, and value in peer review. Future studies will explore integrating this model into a digital platform for reviewing and curating scientific discoveries to improve the production and dissemination of high-quality research.

scientific communication and education↗

bioRxiv2024

Chronic Toxoplasma gondii infection curtails the cytotoxic potential of acute T cell responses to West Nile virus in the brain.

Toxoplasma gondii (T. gondii), a common brain-tropic parasite, chronically infects the central nervous system (CNS) of up to a third of the worlds population. Constant immune surveillance interrupts cyst reactivation within the CNS and dramatically alters the immune landscape of the brain. West Nile virus (WNV) is a mosquito-borne infection with a clinical spectrum ranging from asymptomatic to mild flu-like symptoms to severe neuroinvasive disease. In a cohort of WNV infected people, we discovered a positive correlation between WNV disease severity and T. gondii seropositivity. In a mouse model pairing chronic T. gondii with acute WNV infection, we found an increased susceptibility of mice to WNV, with reduced granzyme B expression in WNV-specific T cells and increased regulatory T cell (Treg) numbers in the brain, but not the periphery. This demonstrates that the T. gondii-infected tissue microenvironment impairs immune defense against other brain infections by blunting local T cell responses.

immunology↗

bioRxiv2023

The CD4 transmembrane GGXXG and juxtamembrane (C/F)CV+C motifs mediate pMHCII-specific signaling independently of CD4-Lck interactions

CD4+ T cell activation is driven by 5-module receptor complexes. The T cell receptor (TCR) is the receptor module that binds composite surfaces of peptide antigens embedded within MHCII molecules (pMHCII). It associates with three signaling modules (CD3{gamma}{varepsilon}, CD3{delta}{varepsilon}, and CD3{zeta}{zeta}) to form TCR-CD3 complexes. CD4 is the coreceptor module. It reciprocally associates with TCR-CD3-pMHCII assemblies on the outside of a CD4+ T cells and with the Src kinase, LCK, on the inside. Previously, we reported that the CD4 transmembrane GGXXG and cytoplasmic juxtamembrane (C/F)CV+C motifs found in eutherian (placental mammal) CD4 have constituent residues that evolved under purifying selection (Lee, et al., 2022). Expressing mutants of these motifs together in T cell hybridomas increased CD4-LCK association but reduced CD3{zeta}, ZAP70, and PLC{gamma}1 phosphorylation levels, as well as IL-2 production, in response to agonist pMHCII. Because these mutants preferentially localized CD4-LCK pairs to non-raft membrane fractions, one explanation for our results was that they impaired proximal signaling by sequestering LCK away from TCR-CD3. An alternative hypothesis is that the mutations directly impacted signaling because the motifs normally play an LCK-independent role in signaling. The goal of this study was to discriminate between these possibilities. Using T cell hybridomas, our results indicate that: intracellular CD4-LCK interactions are not necessary for pMHCII-specific signal initiation; the GGXXG and (C/F)CV+C motifs are key determinants of CD4-mediated pMHCII-specific signal amplification; the GGXXG and (C/F)CV+C motifs exert their functions independently of direct CD4-LCK association. These data provide a mechanistic explanation for why residues within these motifs are under purifying selection in jawed vertebrates. The results are also important to consider for biomimetic engineering of synthetic receptors.

immunology↗

bioRxiv2022

The TCR Cα domain regulates responses to self-pMHCII

T-cells play a central role in adaptive immunity by recognizing peptide-antigens presented in MHC molecules (pMHC) via their clonotypic T-cell receptors (TCRs). {beta}TCRs are heterodimers, consisting of TCR and TCR{beta} subunits that are composed of variable (V, V{beta}) and constant (C, C{beta}) domains. While the V, V{beta}, and C{beta} domains adopt typical immunoglobulin (Ig) folds in the extracellular space, the C domain lacks a top {beta} sheet and instead has two loosely associated top strands (C and F strands) on its surface. Previous results suggest that this unique Ig-like fold mediates homotypic TCR interactions and influences signaling in vitro. To better understand why evolution has selected this unique structure, we asked: what is the fitness cost for development and function of CD4+ T cells bearing a mutation in the C C-strand? In both TCR retrogenic and transgenic mice we observed increased single positive thymocytes bearing mutant TCRs compared with those expressing wild type TCRs. Furthermore, our analysis of mutant TCR transgenic mice revealed an increase in naive CD4+ T cells experiencing strong tonic TCR signals, increased homeostatic survival, and increased recruitment of responders to cognate pMHCII upon immunization, compared to wild type. The mutation did not, however, overtly impact CD4+ T cell proliferation or differentiation after immunization. We interpret these data as evidence that the unique C domain has evolved to fine-tune TCR signaling, particularly in response to weak interactions with self-pMHCII.

immunology↗

bioRxiv2021

Enhancing and inhibitory motifs have coevolved to regulate CD4 activity

CD4+ T cells use T cell receptor (TCR)-CD3 complexes, and CD4, to respond to peptide antigens within MHCII molecules (pMHCII). We report here that, through [~]435 million years of evolution in jawed vertebrates, purifying selection has shaped motifs in the extracellular, transmembrane, and intracellular domains of eutherian CD4 that both enhance pMHCII responses and are coevolving with residues in an intracellular motif that inhibits pMHCII responses. Importantly, while CD4 interactions with the Src kinase, Lck, are classically viewed as the key determinant of CD4s contribution to pMHCII responses, we found that without the inhibitory motif CD4-Lck interactions are not necessary for robust responses to pMHCII. In summary, motifs that mediate events on the outside and inside of CD4+ T cells coevolved to finetune the relay of pMHCII-specific information across the membrane. These results have implications for the evolution and function of complex transmembrane receptors and for biomimetic engineering.

immunology↗

bioRxiv2020

A biomimetic five-module chimeric antigen receptor (5MCAR) designed to target and eliminate antigen-specific T cells

T cells express clonotypic T cell receptors (TCRs) that recognize peptide antigens in the context of class I or II MHC molecules (pMHCI/II). These receptor modules associate with three signaling modules (CD3{gamma}{varepsilon}, {delta}{varepsilon}, and {zeta}{zeta}), and work in concert with a coreceptor module (either CD8 or CD4), to drive T cell activation in response to pMHCI/II. Here we describe a first generation biomimetic 5-module chimeric antigen receptor (5MCAR). We show that: (i) chimeric receptor modules built with the ectodomains of pMHCII assemble with CD3 signaling modules into complexes that redirect cytotoxic T lymphocyte (CTL) specificity and function in response to the clonotypic TCRs of pMHCII-specific CD4+ T cells; and, (ii) surrogate coreceptor modules enhance the function of these complexes. Furthermore, we demonstrate that adoptively transferred 5MCAR-CTLs can mitigate type I diabetes by targeting autoimmune CD4+ T cells in NOD mice. This work provides a framework for the construction of biomimetic 5MCARs that can be used as tools to study the impact of particular antigen-specific T cells in immune responses, and may hold potential for ameliorating diseases mediated by pathogenic T cells.

bioengineering↗