About InVivoMAb anti-rat CD45RC (OX22) The OX-22 antibody reacts with CD45RC, an exon 5 splice variant (exon C) of the tyrosine phosphatase CD45. Distinct molecular weight isoforms of CD45 result from the differential splicing of three exons (A, B, and C) encoding a portion of the N-terminal extracellular domain. CD45RC is a single-chain type I membrane glycoprotein, and it is expressed on B cells, the majority of CD8+ T cells, and about three-quarters of CD4+ T cells, but not on myeloid cells. From a functional perspective, the CD45RC molecule is involved in lymphocyte signaling and is associated with inflammatory responses (e.g., defective IL-2 production in Long-Evans Cinnamon rats' peripheral CD4+ T cells). CD45RC expression levels in rats define CD4 T cells to have two different functional subpopulations with unique cytokine profiles, i.e., CD45RChigh or CD45RClow. The OX22 antibody is commonly used as a CD45RC marker to detect and isolate these sub-populations. In some in vivo studies, the antibody is also used to deplete CD45RChigh subsets. CD45RClow T cells exhibit strong immunoregulatory properties, particularly in Tregs, while memory T cells can be found in both CD45RChigh and CD45RClow subsets. CD45RC is a promising target in preclinical immunotherapy studies, and its precise targeting helps to manage severe immune-mediated conditions like Graft-versus-Host Disease (GvHD) and autoimmune diseases without compromising beneficial anti-tumor or antiviral immunity. InVivoMAb anti-rat CD45RC (OX22) Specifications IsotypeMouse IgG1, κ Recommended Isotype Control(s)InVivoMAb mouse IgG1 isotype control, unknown specificity Recommended Dilution BufferInVivoPure pH 7.0 Dilution Buffer ImmunogenPhytohemagglutinin-activated rat lymph node cells Reported Applicationsin vivo depletion of CD45RChigh cells ex vivo depletion of CD45RChigh cells in vitro selection of CD45RC+ cells in vitro functional assay Immunohistochemistry (frozen) Immunohistochemistry (paraffin) Immunofluorescence Flow cytometry FormulationPBS, pH 7.0 Contains no stabilizers or preservatives Endotoxin≤1EU/mg (≤0.001EU/μg)Determined by LAL gel clotting assay Purity≥95% Determined by SDS-PAGE Sterility0.2 μm filtered ProductionPurified from cell culture supernatant in an animal-free facility PurificationProtein G Molecular Weight150 kDa StorageThe antibody solution should be stored at the stock concentration at 4°C. Do not freeze. Application ReferencesInVivoMAb anti-rat CD45RC (OX22) (CLONE: OX-22)Boucault L, Lopez Robles MD, Thiolat A, Bézie S, Schmueck-Henneresse M, Braudeau C, Vimond N, Freuchet A, Autrusseau E, Charlotte F, Redjoul R, Beckerich F, Leclerc M, Piaggio E, Josien R, Volk HD, Maury S, Cohen JL, Anegon I, Guillonneau C (2020). "Transient antibody targeting of CD45RC inhibits the development of graft-versus-host disease" Blood Adv 4(11):2501-2515. PubMedAllogeneic bone marrow transplantation (BMT) is a widely spread treatment of many hematological diseases, but its most important side effect is graft-versus-host disease (GVHD). Despite the development of new therapies, acute GVHD (aGVHD) occurs in 30% to 50% of allogeneic BMT and is characterized by the generation of effector T (Teff) cells with production of inflammatory cytokines. We previously demonstrated that a short anti-CD45RC monoclonal antibody (mAb) treatment in a heart allograft rat model transiently decreased CD45RChigh Teff cells and increased regulatory T cell (Treg) number and function allowing long-term donor-specific tolerance. Here, we demonstrated in rat and mouse allogeneic GVHD, as well as in xenogeneic GVHD mediated by human T cells in NSG mice, that both ex vivo depletion of CD45RChigh T cells and in vivo treatment with short-course anti-CD45RC mAbs inhibited aGVHD. In the rat model, we demonstrated that long surviving animals treated with anti-CD45RC mAbs were fully engrafted with donor cells and developed a donor-specific tolerance. Finally, we validated the rejection of a human tumor in NSG mice infused with human cells and treated with anti-CD45RC mAbs. The anti-human CD45RC mAbs showed a favorable safety profile because it did not abolish human memory antiviral immune responses, nor trigger cytokine release in in vitro assays. Altogether, our results show the potential of a prophylactic treatment with anti-human CD45RC mAbs in combination with rapamycin as a new therapy to treat aGVHD without abolishing the antitumor effect.
