CD8+ T cells mediate antibody-independent platelet clearance in mice

Abstract

• Previous studies suggest that immune-mediated platelet clearance following transfusion represents an antibody-mediated process.• The results of this study demonstrate that CD8 1T cells can mediate platelet clearance independent of anti-platelet alloantibodies.Platelet transfusion provides an important therapeutic intervention in the treatment and prevention of bleeding. However, some patients rapidly clear transfused platelets, preventing the desired therapeutic outcome. Although platelet clearance can occur through a variety of mechanisms, immune-mediated platelet removal often plays a significant role. Numerous studies demonstrate that anti-platelet alloantibodies can induce significant platelet clearance following transfusion. In fact, for nearly 50 years, anti-platelet alloantibodies were considered to be the sole mediator of immune-mediated platelet clearance in plateletrefractory individuals. Although nonimmune mechanisms of platelet clearance can often explain platelet removal in the absence of anti-platelet alloantibodies, many patients experience platelet clearance following transfusion in the absence of a clear mechanism. These results suggest that other processes of antibody-independent platelet clearance may occur. Our studies demonstrate that CD8 1 T cells possess the unique ability to induce platelet clearance in the complete absence of antiplatelet alloantibodies. These results suggest a previously unrecognized form of immune-mediated platelet clearance with significant implications in the appropriate management of platelet-refractory individuals.

Antigen Density Dictates Immune Responsiveness following Red Blood Cell Transfusion

“…B cell–deficient μMT (C57BL/6- Ighm tm1Cgn / J) mice were purchased from the Jackson Laboratory (Bar Harbor, ME) and maintained as described previously (19). IL-10–GFP/Vert-x [C57BL/6(Cg)- IL10 tm1.1Karp / J] and Foxp3-RFP (C57BL/6- Foxp3 tm1Flv / J) recipients were generous gifts from Dr. J. Galipeau and Dr. E. Waller, respectively (20).…”

“…To determine the level of anti-HOD or anti-KEL Ab formation at various time points following RBC challenge, we used a flow cross match approach, as described previously (17, 19). Briefly, to detect anti-KEL Abs bound to KEL RBCs, samples were next incubated with allophycocyanin goat anti-IgG or FITC goat anti-IgM diluted 1:100 in FACS buffer for 30 min at 4°C.…”

Daratumumab (anti-CD38) induces loss of CD38 on red blood cells

“…Consistent with these and previous results, 8,9,12,13 DARA also failed to cause significant anemia, suggesting minimal (if any) DARA-mediated hemolysis ( Figure 1A). To more specifically investigate the interaction between DARA and RBCs, we examined antibody reactivity on the RBC surface using a more sensitive flow cytometrybased DAT in which antibody engagement of RBCs is assessed using fluorescently labeled anti-human immunoglobulin G. 14,15 RBCs isolated from DARA-treated patients demonstrated weak antibody positivity when compared with RBCs isolated from nontreated patients ( Figure 1B incubated RBCs from DARA-treated or nontreated patients with saturating levels of DARA. RBCs from nontreated patients displayed higher DARA engagement than RBCs from DARA-treated individuals ( Figure 1C), strongly suggesting that the reduced DAT level following DARA treatment did not reflect incomplete CD38 binding but instead possibly reflected an actual loss of the CD38 target antigen.…”

Antibody‐mediated immunosuppression can result from RBC antigen loss independent of Fcγ receptors in mice

“…For detection of Ter‐119, RBCs were stained with Ter‐119 (BD Biosciences), as done previously . To assess anti‐HOD immunoglobulin M (IgM) and IgG antibody development, sera were flow cross‐matched, as previously described . All antibodies were used at 1:100 in fluorescence activated cell sorting buffer (2% bovine serum albumin in phosphate‐buffered saline) unless otherwise noted, as done previously …”