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Product Description

The 37.51 monoclonal antibody reacts with mouse CD28, a 45 kDa costimulatory receptor and a member of the Ig superfamily. CD28 is expressed by thymocytes, most peripheral T cells, and NK cells. CD28 is a receptor for CD80 (B7-1) and CD86 (B7-2). Signaling through CD28 augments IL-2 and IL-2 receptor expression as well as cytotoxicity of CD3-activated T cells. The 37.51 antibody has been shown to stimulate the proliferation and cytokine production by activated T and NK cells and provide a costimulatory signal for CTL induction.

Specifications

Isotype Syrian Hamster IgG2
Recommended Isotype Control(s) InVivoMAb polyclonal Syrian hamster IgG
Recommended Dilution Buffer InVivoPure pH 6.0T Dilution Buffer
Conjugation This product is unconjugated. Conjugation is available via our Antibody Conjugation Services.
Immunogen C57BL/6 mouse T cell lymphoma EL-4 cells
Reported Applications in vitro T cell stimulation/activation
in vivo CD28 blockade
Formulation PBS, pH 6.0
0.01% Tween


Contains no stabilizers or preservatives
Endotoxin ≤1EU/mg (≤0.001EU/μg)
Determined by LAL assay
Purity ≥95%
Determined by SDS-PAGE
Sterility 0.2 µm filtration
Production Purified from cell culture supernatant in an animal-free facility
Purification Protein G
RRID AB_1107624
Molecular Weight 150 kDa
Storage The antibody solution should be stored at the stock concentration at 4°C. Do not freeze.
Need a Custom Formulation? See All Antibody Customization Options

Application References

  • in vitro T cell stimulation/activation
    Tang, W., et al (2014). "The oncoprotein and transcriptional regulator Bcl-3 governs plasticity and pathogenicity of autoimmune T cells" Immunity 41(4): 555-566.

    Bcl-3 is an atypical member of the IkappaB family that modulates transcription in the nucleus via association with p50 (NF-kappaB1) or p52 (NF-kappaB2) homodimers. Despite evidence attesting to the overall physiologic importance of Bcl-3, little is known about its cell-specific functions or mechanisms. Here we demonstrate a T-cell-intrinsic function of Bcl-3 in autoimmunity. Bcl-3-deficient T cells failed to induce disease in T cell transfer-induced colitis and experimental autoimmune encephalomyelitis. The protection against disease correlated with a decrease in Th1 cells that produced the cytokines IFN-gamma and GM-CSF and an increase in Th17 cells. Although differentiation into Th1 cells was not impaired in the absence of Bcl-3, differentiated Th1 cells converted to less-pathogenic Th17-like cells, in part via mechanisms involving expression of the RORgammat transcription factor. Thus, Bcl-3 constrained Th1 cell plasticity and promoted pathogenicity by blocking conversion to Th17-like cells, revealing a unique type of regulation that shapes adaptive immunity.

  • in vitro T cell stimulation/activation
    Rabenstein, H., et al (2014). "Differential kinetics of antigen dependency of CD4+ and CD8+ T cells" J Immunol 192(8): 3507-3517.

    Ag recognition via the TCR is necessary for the expansion of specific T cells that then contribute to adaptive immunity as effector and memory cells. Because CD4+ and CD8+ T cells differ in terms of their priming APCs and MHC ligands we compared their requirements of Ag persistence during their expansion phase side by side. Proliferation and effector differentiation of TCR transgenic and polyclonal mouse T cells were thus analyzed after transient and continuous TCR signals. Following equally strong stimulation, CD4+ T cell proliferation depended on prolonged Ag presence, whereas CD8+ T cells were able to divide and differentiate into effector cells despite discontinued Ag presentation. CD4+ T cell proliferation was neither affected by Th lineage or memory differentiation nor blocked by coinhibitory signals or missing inflammatory stimuli. Continued CD8+ T cell proliferation was truly independent of self-peptide/MHC-derived signals. The subset divergence was also illustrated by surprisingly broad transcriptional differences supporting a stronger propensity of CD8+ T cells to programmed expansion. These T cell data indicate an intrinsic difference between CD4+ and CD8+ T cells regarding the processing of TCR signals for proliferation. We also found that the presentation of a MHC class II-restricted peptide is more efficiently prolonged by dendritic cell activation in vivo than a class I bound one. In summary, our data demonstrate that CD4+ T cells require continuous stimulation for clonal expansion, whereas CD8+ T cells can divide following a much shorter TCR signal.

  • in vitro T cell stimulation/activation
    Gu, A. D., et al (2015). "A critical role for transcription factor Smad4 in T cell function that is independent of transforming growth factor beta receptor signaling" Immunity 42(1): 68-79.

    Transforming growth factor-beta (TGF-beta) suppresses T cell function to maintain self-tolerance and to promote tumor immune evasion. Yet how Smad4, a transcription factor component of TGF-beta signaling, regulates T cell function remains unclear. Here we have demonstrated an essential role for Smad4 in promoting T cell function during autoimmunity and anti-tumor immunity. Smad4 deletion rescued the lethal autoimmunity resulting from transforming growth factor-beta receptor (TGF-betaR) deletion and compromised T-cell-mediated tumor rejection. Although Smad4 was dispensable for T cell generation, homeostasis, and effector function, it was essential for T cell proliferation after activation in vitro and in vivo. The transcription factor Myc was identified to mediate Smad4-controlled T cell proliferation. This study thus reveals a requirement of Smad4 for T-cell-mediated autoimmunity and tumor rejection, which is beyond the current paradigm. It highlights a TGF-betaR-independent role for Smad4 in promoting T cell function, autoimmunity, and anti-tumor immunity.

  • in vitro T cell stimulation/activation
    Choi, Y. S., et al (2015). "LEF-1 and TCF-1 orchestrate TFH differentiation by regulating differentiation circuits upstream of the transcriptional repressor Bcl6" Nat Immunol 16(9): 980-990.

    Follicular helper T cells (TFH cells) are specialized effector CD4(+) T cells that help B cells develop germinal centers (GCs) and memory. However, the transcription factors that regulate the differentiation of TFH cells remain incompletely understood. Here we report that selective loss of Lef1 or Tcf7 (which encode the transcription factor LEF-1 or TCF-1, respectively) resulted in TFH cell defects, while deletion of both Lef1 and Tcf7 severely impaired the differentiation of TFH cells and the formation of GCs. Forced expression of LEF-1 enhanced TFH differentiation. LEF-1 and TCF-1 coordinated such differentiation by two general mechanisms. First, they established the responsiveness of naive CD4(+) T cells to TFH cell signals. Second, they promoted early TFH differentiation via the multipronged approach of sustaining expression of the cytokine receptors IL-6Ralpha and gp130, enhancing expression of the costimulatory receptor ICOS and promoting expression of the transcriptional repressor Bcl6.

Product Citations

  • S1P-S1PR1 signaling impairs CD8+ T cell metabolism and effector function in tumors.

    In EMBO Rep on 1 April 2026 by Basak, D., Ghosh, P., et al.

    PubMed

    Sphingosine-1-phosphate receptor 1 (S1PR1) signaling has been linked to the regulation of immunosuppressive cell populations within the tumor microenvironment (TME); however, its role in shaping anti-tumor CD8⁺ T cell responses remains poorly defined. Herein, we demonstrate that intratumoral CD8⁺ T cells express S1PR1, with expression predominantly enriched in the terminally exhausted subset. Transcriptomic profiling, combined with pharmacological inhibition and genetic knockdown, reveals that S1PR1-S1P signaling activates the PERK (protein kinase R (PKR)-like endoplasmic reticulum kinase)-CHOP (C/EBP homologous protein) axis of the endoplasmic reticulum stress response. CHOP, in turn, upregulates transcription of Map3k13 and Map3k15, triggering downstream MAPK signaling and culminating in activation of p38MAPK. Activation of this pathway impairs CD8⁺ T cell metabolism and effector function while increasing apoptotic susceptibility. This ultimately limits the persistence and accumulation of functional CD8⁺ T cells within the TME, thereby compromising their responsiveness to anti-PD-1 therapy. Targeting the S1PR1-S1P axis or its downstream effectors offers a promising strategy to improve cancer immunotherapy outcomes.

  • SLC7A5 regulates B cell metabolism and plasma cell differentiation independent of leucine transport.

    In J Immunol on 17 March 2026 by Tao, A. Y., Hu, K., et al.

    PubMed

    B cells play critical roles in humoral immunity to infection, vaccination, and autoimmunity. The differentiation of B cells into antibody-producing plasma cells (PCs) has been extensively studied, but the role of metabolic transporters that mediate nutrient uptake during PC differentiation is not well-understood. Here, we characterized the dependence of B cells and PC differentiation on the neutral amino acid transporter SLC7A5. We demonstrate that SLC7A5 promotes B cell functions including proliferation and PC differentiation in vitro and in vivo after immunization with T dependent and independent antigens. Deletion of SLC7A5 in B cells suppressed the function of mTORC1 and enforced mTORC1 activity rescued PC differentiation. The role of SLC7A5 in B cells appears to be unrelated to leucine uptake because B cells were insensitive to extracellular leucine depletion. Defects in SLC7A5-deficient B cells could, however, be rescued by extracellular methionine supplementation, suggesting a role for methionine in SLC7A5-dependent B cell function and PC differentiation. Our study provides evidence for a leucine-independent role of SLC7A5 in B cell function and PC differentiation.

  • Spatial tumor evolution panorama of ovarian cancer.

    In Cell Rep Med on 17 March 2026 by Feng, C., Yang, Y., et al.

    PubMed

    Ovarian cancer is an aggressive disease characterized by intraperitoneal dissemination and a distinctive microenvironment. By generating metastatic cohorts encompassing approximately 60 pairs of whole-genome and RNA sequencing, 100 single-cell samples, and 2.5 million spatial transcriptomics (ST) spots, we delineate site-specific tumor-host colocalization patterns. Utilizing our STARLETS framework, we elucidate a Darwinian evolutionary trajectory in which hypoxia and immune pressures select for clones that eventually metastasize. High-resolution ST and ultimate dimensional imaging of solvent-cleared organs (uDISCO) imaging further identify a tripartite ensemble comprising MMP11+ myCAFs, epithelial cells, and SPP1+ macrophages in ascites and metastases, which can be modulated via SPP1-CD44 inhibition. SPP1+ macrophages predict therapeutic responses in clinical trials, including oncolytic virus and poly(ADP-ribose) polymerase inhibitor treatments. Collectively, our study advances insights into spatial dynamics that hold promise for therapeutic approaches in ovarian cancer.

  • Facile induction of immune tolerance by an interleukin-2-TGFβ surrogate agonist.

    In Nature on 11 March 2026 by Sun, Q., Barrett, A. K., et al.

    PubMed

    CD4+ regulatory T cells (Treg cells) are essential for immune tolerance1. Peripherally induced Treg cells (pTreg cells) complement thymic Treg cells by broadening Treg cell reactivity in response to a changing antigenic landscape2. Although both TGFβ and IL-2 synergistically promote functional pTreg cell development in vitro3-6, their combined roles in inducing pTreg cell generation in vivo have not been exploited for tolerizing immunotherapy. Here we designed an IL-2-TGFβ 'surrogate' co-agonist by creating a single-chain fusion protein between IL-2 and a low-affinity TGFβ mimic agonist derived from a helminth parasite7. This IL-2-TGFβ surrogate functions as an AND-gated co-agonist and enabled simultaneous cis-activation of IL-2-STAT5 and TGFβ-SMAD2/3 signalling specifically in T cells that express IL-2 receptors. The IL-2-TGFβ surrogate agonist robustly induced antigen-specific, functional and stable pTreg cells in vivo within peripheral lymphoid organs in mice immunized with ovalbumin (OVA) and myelin oligodendrocyte glycoprotein (MOG)35-55. The induced pTreg cells display an effector-like, actively expanding state with high RORγt expression, enabling efficient migration and suppression of intestinal inflammation. Treatment with this agonist effectively quelled immune activation in mouse models of allergen-induced allergic inflammation and self-antigen-driven autoimmune neuroinflammation, suggesting a strategy for the induction of antigen-specific pTreg cells in vivo to establish immune tolerance in inflammatory, allergic and autoimmune diseases.

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