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Product Description

The L243 monoclonal antibody reacts with the human and monkey MHC class II, HLA-DR. HLA-DR is a transmembrane glycoprotein composed of an α chain (36 kDa) and a β chain (27 kDa). HLA-DR is expressed primarily on antigen presenting cells such as B cells, monocytes, macrophages, thymic epithelial cells and activated T cells. HLA-DR is critical for the presentation of peptides to CD4+ T cells.

Specifications

Isotype Mouse IgG2a, κ
Recommended Isotype Control(s) InVivoMAb mouse IgG2a isotype control, unknown specificity
Recommended Dilution Buffer InVivoPure pH 7.0 Dilution Buffer
Conjugation This product is unconjugated. Conjugation is available via our Antibody Conjugation Services.
Immunogen Human lymphoblastoid B cell line RPMI 8866.9
Reported Applications in vitro blocking of MHC class II HLA-DR
HLA class II binding assay
in vitro MHC class II HLA-DR expressing cell negative selection
Western blot
Flow cytometry
Immunopeptidomics
Formulation PBS, pH 7.0
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_2736986
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

  • Immunopeptidomics
    Mori S, Kohyama M, Yasumizu Y, Tada A, Tanzawa K, Shishido T, Kishida K, Jin H, Nishide M, Kawada S, Motooka D, Okuzaki D, Naito R, Nakai W, Kanda T, Murata T, Terao C, Ohmura K, Arase N, Kurosaki T, Fujimoto M, Suenaga T, Kumanogoh A, Sakaguchi S, O

    Major histocompatibility complex class II (MHC-II) is the most significant genetic risk factor for systemic lupus erythematosus (SLE), but the nature of the self-antigens that trigger autoimmunity remains unclear. Unusual self-antigens, termed neoself-antigens, are presented on MHC-II in the absence of the invariant chain essential for peptide presentation. Here, we demonstrate that neoself-antigens are the primary target for autoreactive T cells clonally expanded in SLE. When neoself-antigen presentation was induced by deleting the invariant chain in adult mice, neoself-reactive T cells were clonally expanded, leading to the development of lupus-like disease. Furthermore, we found that neoself-reactive CD4+ T cells were significantly expanded in SLE patients. A high frequency of Epstein-Barr virus reactivation is a risk factor for SLE. Neoself-reactive lupus T cells were activated by Epstein-Barr-virus-reactivated cells through downregulation of the invariant chain. Together, our findings imply that neoself-antigen presentation by MHC-II plays a crucial role in the pathogenesis of SLE.

  • Immunopeptidomics
    Bourne CM, Mun SS, Dao T, Aretz ZEH, Molvi Z, Gejman RS, Daman A, Takata K, Steidl C, Klatt MG, Scheinberg DA (2022). "Unmasking the suppressed immunopeptidome of EZH2-mutated diffuse large B-cell lymphomas through combination drug treatment" Blood A

    Exploring the repertoire of peptides presented on major histocompatibility complexes (MHCs) helps identify targets for immunotherapy in many hematologic malignancies. However, there is a paucity of such data for diffuse large B-cell lymphomas (DLBCLs), which might be explained by the profound downregulation of MHC expression in many DLBCLs, and in particular in the enhancer of zeste homolog 2 (EZH2)-mutated subgroup. Epigenetic drug treatment, especially in the context of interferon-γ (IFN-γ), restored MHC expression in DLBCL. In DLBCL, peptides presented on MHCs were identified via mass spectrometry after treatment with tazemetostat or decitabine alone or in combination with IFN-γ. Such treatment synergistically increased the expression of MHC class I surface proteins up to 50-fold and the expression of class II surface proteins up to threefold. Peptides presented on MHCs increased to a similar extent for both class I and class II MHCs. Overall, these treatments restored the diversity of the immunopeptidome to levels described in healthy B cells for 2 of 3 cell lines and allowed the systematic search for new targets for immunotherapy. Consequently, we identified multiple MHC ligands from the regulator of G protein signaling 13 (RGS13) and E2F transcription factor 8 (E2F8) on different MHC alleles, none of which have been described in healthy tissues and therefore represent tumor-specific MHC ligands that are unmasked only after drug treatment. Overall, our results show that EZH2 inhibition in combination with decitabine and IFN-γ can expand the repertoire of MHC ligands presented on DLBCLs by revealing suppressed epitopes, thus allowing the systematic analysis and identification of new potential immunotherapy targets.

  • in vitro blocking of MHC class II HLA-DR
    Brentville, V. A., et al (2016). "Citrullinated Vimentin Presented on MHC-II in Tumor Cells Is a Target for CD4+ T-Cell-Mediated Antitumor Immunity" Cancer Res 76(3): 548-560.

    Stressful conditions in the harsh tumor microenvironment induce autophagy in cancer cells as a mechanism to promote their survival. However, autophagy also causes post-translational modification of proteins that are recognized by the immune system. In particular, modified self-antigens can trigger CD4(+) T-cell responses that might be exploited to boost antitumor immune defenses. In this study, we investigated the ability of CD4 cells to target tumor-specific self-antigens modified by citrullination, which converts arginine residues in proteins to citrulline. Focusing on the intermediate filament protein vimentin, which is frequently citrullinated in cells during epithelial-to-mesenchymal transition of metastasizing epithelial tumors, we generated citrullinated vimentin peptides for immunization experiments in mice. Immunization with these peptides induced IFNgamma- and granzyme B-secreting CD4 T cells in response to autophagic tumor targets. Remarkably, a single immunization with modified peptide, up to 14 days after tumor implant, resulted in long-term survival in 60% to 90% of animals with no associated toxicity. This antitumor response was dependent on CD4 cells and not CD8(+) T cells. These results show how CD4 cells can mediate potent antitumor responses against modified self-epitopes presented on tumor cells, and they illustrate for the first time how the citrullinated peptides may offer especially attractive vaccine targets for cancer therapy.

  • in vitro blocking of MHC class II HLA-DR
    Brentville, V. A., et al (2016). "Citrullinated Vimentin Presented on MHC-II in Tumor Cells Is a Target for CD4+ T-Cell-Mediated Antitumor Immunity" Cancer Res 76(3): 548-560.

    Stressful conditions in the harsh tumor microenvironment induce autophagy in cancer cells as a mechanism to promote their survival. However, autophagy also causes post-translational modification of proteins that are recognized by the immune system. In particular, modified self-antigens can trigger CD4(+) T-cell responses that might be exploited to boost antitumor immune defenses. In this study, we investigated the ability of CD4 cells to target tumor-specific self-antigens modified by citrullination, which converts arginine residues in proteins to citrulline. Focusing on the intermediate filament protein vimentin, which is frequently citrullinated in cells during epithelial-to-mesenchymal transition of metastasizing epithelial tumors, we generated citrullinated vimentin peptides for immunization experiments in mice. Immunization with these peptides induced IFNgamma- and granzyme B-secreting CD4 T cells in response to autophagic tumor targets. Remarkably, a single immunization with modified peptide, up to 14 days after tumor implant, resulted in long-term survival in 60% to 90% of animals with no associated toxicity. This antitumor response was dependent on CD4 cells and not CD8(+) T cells. These results show how CD4 cells can mediate potent antitumor responses against modified self-epitopes presented on tumor cells, and they illustrate for the first time how the citrullinated peptides may offer especially attractive vaccine targets for cancer therapy.

Product Citations

  • Single-Cell Sequencing Reveals That CD4+ T Cells Eliminate Senescent Prostate Epithelium to Delay Progression of Benign Prostatic Hyperplasia.

    In Aging Cell on 1 October 2025 by Li, Z., Wang, X., et al.

    PubMed

    Benign prostatic hyperplasia (BPH) is an age-related condition characterized by progressive prostate enlargement driven in part by the accumulation of senescent epithelial cells and their pro-inflammatory secretome. Using human single-cell RNA sequencing and laser capture microdissection, we identified C-X-C Motif Chemokine Ligand 13 (CXCL13) as a key chemokine secreted by senescent prostate epithelial cells. CXCL13 recruits CD4+ T cells via the C-X-C Chemokine Receptor Type 5 (CXCR5) receptor, facilitating immune recognition through human leukocyte antigen-DR isotype (HLA-DR) and promoting senescent cell clearance. Functional assays revealed that CD4+ cytotoxic T lymphocytes (CTLs) mediate this clearance, while regulatory T cells (Tregs) suppress it, forming a functional dichotomy. Immunohistochemistry, transwell migration, and co-culture assays confirmed this CXCL13-CXCR5-HLA-DR axis. In a testosterone-induced BPH mouse model, CXCL13 treatment enhanced CD4+ T cell infiltration and reduced epithelial senescence, while CD4+ T cell depletion reversed these effects. Single-cell transcriptomics in mice further validated increased CXCL13 expression and CD4+ T cell engagement. These findings uncover a critical immune surveillance mechanism in BPH and suggest that targeting the CXCL13-CD4+ T cell axis may offer a novel therapeutic strategy for age-related prostate enlargement.

  • ALS-associated TDP-43 aggregates drive innate and adaptive immune cell activation.

    In iScience on 20 June 2025 by Evangelista, B. A., Ragusa, J. V., et al.

    PubMed

    Amyotrophic lateral sclerosis (ALS) is the most common and fatal motor neuron disease. Approximately 90% of ALS patients exhibit pathology of the master RNA regulator, transactive response DNA binding protein (TDP-43). Despite the prevalence TDP-43 pathology in ALS motor neurons, recent findings suggest immune dysfunction is a determinant of disease progression in patients. Whether TDP-43 aggregates elicit immune responses remains underexplored. In this study, we demonstrate that TDP-43 aggregates are internalized by antigen-presenting cell populations, cause vesicle rupture, and drive innate and adaptive immune cell activation by way of antigen presentation. Using a multiplex imaging platform, we observed enrichment of activated microglia/macrophages in ALS white matter that correlated with phosphorylated TDP-43 accumulation, CD8 T cell infiltration, and major histocompatibility complex expression. Taken together, this study sheds light on a novel cellular response to TDP-43 aggregates through an immunological lens.

  • Interferon-γ-stimulated antigen-presenting cancer-associated fibroblasts hinder neoadjuvant chemoimmunotherapy efficacy in lung cancer.

    In Cell Rep Med on 18 March 2025 by Cao, Z., Meng, Z., et al.

    PubMed

    Conventional neoadjuvant chemotherapy provides limited benefit for patients with resectable non-small cell lung cancer (NSCLC). Recently, neoadjuvant chemoimmunotherapy (NCIT) has transformed the perioperative management of NSCLC by priming systemic anti-tumor immunity before surgery, yet it remains ineffective for at least 50% of patients. Through single-cell sequencing analysis of our NCIT cohort, we identify that antigen-presenting cancer-associated fibroblasts (apCAFs) can impede the efficacy of NCIT. Using a custom cancer-associated fibroblast biobank, we uncover that interferon (IFN)-γ stimulates apCAF expansion via the JAK1/2-STAT1-IFI6/27 pathway. Mechanistically, apCAFs significantly contribute to PD-L2 expression in the tumor microenvironment (TME), triggering the accumulation of FOXP1+regulatory T cells (Tregs) through the PD-L2-RGMB axis. Reprogramming apCAFs by inhibiting the IFN-γ pathway or blocking the PD-L2-RGMB axis substantially mitigates apCAFs-mediated FOXP1+Tregs' expansion. In summary, we reveal the role of apCAFs in compromising NCIT efficacy and propose applications for anti-PD-L2/RGMB regimens to synergize with anti-PD1 therapies by targeting apCAFs.

  • Characterizations of a neutralizing antibody broadly reactive to multiple gluten peptide:HLA-DQ2.5 complexes in the context of celiac disease.

    In Nat Commun on 22 December 2023 by Okura, Y., Ikawa-Teranishi, Y., et al.

    PubMed

    In human celiac disease (CeD) HLA-DQ2.5 presents gluten peptides to antigen-specific CD4+ T cells, thereby instigating immune activation and enteropathy. Targeting HLA-DQ2.5 with neutralizing antibody for treating CeD may be plausible, yet using pan-HLA-DQ antibody risks affecting systemic immunity, while targeting selected gluten peptide:HLA-DQ2.5 complex (pHLA-DQ2.5) may be insufficient. Here we generate a TCR-like, neutralizing antibody (DONQ52) that broadly recognizes more than twenty-five distinct gluten pHLA-DQ2.5 through rabbit immunization with multi-epitope gluten pHLA-DQ2.5 and multidimensional optimization. Structural analyses show that the proline-rich and glutamine-rich motif of gluten epitopes critical for pathogenesis is flexibly recognized by multiple tyrosine residues present in the antibody paratope, implicating the mechanisms for the broad reactivity. In HLA-DQ2.5 transgenic mice, DONQ52 demonstrates favorable pharmacokinetics with high subcutaneous bioavailability, and blocks immunity to gluten while not affecting systemic immunity. Our results thus provide a rationale for clinical testing of DONQ52 in CeD.

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