Donor natural killer cells trigger production of ß-2-microglobulin to enhance post-bone marrow transplant immunity.

Allogeneic hematopoietic transplantation is a powerful treatment for hematologic malignancies. Posttransplant immune incompetence exposes patients to disease relapse and infections. We previously demonstrated that donor alloreactive natural killer (NK) cells ablate recipient hematopoietic targets, including leukemia. Here, in murine models, we show that infusion of donor alloreactive NK cells triggers recipient dendritic cells (DCs) to synthesize ß-2-microglobulin (B2M) that elicits the release of c-KIT ligand and interleukin-7 that greatly accelerate posttransplant immune reconstitution. An identical chain of events was reproduced by infusing supernatants of alloreactive NK/DC cocultures. Similarly, human alloreactive NK cells triggered human DCs to synthesize B2M that induced interleukin-7 production by thymic epithelial cells and thereby supported thymocyte cellularity in vitro. Chromatography fractionation of murine and human alloreactive NK/DC coculture supernatants identified a protein with molecular weight and isoelectric point of B2M, and mass spectrometry identified amino acid sequences specific of B2M. Anti-B2M antibody depletion of NK/DC coculture supernatants abrogated their immune-rebuilding effect. B2M knock-out mice were unable to undergo accelerated immune reconstitution, but infusion of (wild-type) NK/DC coculture supernatants restored their ability to undergo accelerated immune reconstitution. Similarly, silencing the B2M gene in human DCs, before coculture with alloreactive NK cells, prevented the increase in thymocyte cellularity in vitro. Finally, human recombinant B2M increased thymocyte cellularity in a thymic epithelial cells/thymocyte culture system. Our studies uncover a novel therapeutic principle for treating posttransplant immune incompetence and suggest that, upon its translation to the clinic, patients may benefit from adoptive transfer of large numbers of cytokine-activated, ex vivo-expanded donor alloreactive NK cells.

Clinical-Grade Expanded Regulatory T Cells Are Enriched with Highly Suppressive Cells Producing IL-10, Granzyme B, and IL-35.

In the setting of T cell-depleted, full-haplotype mismatched transplantation, adoptive immunotherapy with regulatory T cells (Tregs) and conventional T cells (Tcons) can prevent graft-versus-host disease (GVHD) and improve post-transplantation immunologic reconstitution and is associated with a powerful graft-versus-leukemia effect. To improve the purity and the quantity of the infused Tregs, good manufacturing practices (GMP)-compatible expansion protocols are needed. Here we expanded Tregs using an automated, clinical-grade protocol. Cells were extensively characterized in vitro, and their efficiency was tested in vivo in a mouse model. Tregs were selected by CliniMacs (CD4+CD25+, 94.5 ± 6.3%; FoxP3+, 63.7 ± 11.5%; CD127+, 20 ± 3%; suppressive activity, 60 ± 7%), and an aliquot of 100 × 106 was expanded for 14 days using the CliniMACS Prodigy System, obtaining 684 ± 279 × 106 cells (CD4+CD25+, 99.6 ± 0.2%; FoxP3+, 82 ± 8%; CD127+, 1.1 ± 0.8%; suppressive activity, 75 ± 12%). CD39 and CTLA4 expression levels increased from 22.4 ± 12% to 58.1 ± 13.3% (P < .05) and from 20.4 ± 6.7% to 85.4 ± 9.8% (P < .01), respectively. TIM3 levels increased from .4 ± .05% to 29 ± 16% (P < .05). Memory Tregs were the prevalent population, whereas naive Tregs almost disappeared at the end of the culture. mRNA analysis displayed significant increases in CD39, IL-10, granzyme B, and IL-35 levels at the end of culture period (P < .05). Conversely, IFNγ expression decreased significantly by day +14. Expanded Tregs were sorted according to TIM3, CD39, and CD62L expression levels (purity >95%). When sorted populations were analyzed, TIM3+ cells showed significant increases in IL-10 and granzyme B (P < .01) .When expanded Tregs were infused in an NSG murine model, mice that received Tcons only died of GVHD, whereas mice that received both Tcons and Tregs survived without GVHD. GMP grade expanded cells that display phenotypic and functional Treg characteristics can be obtained using a fully automated system. Treg suppression is mediated by multiple overlapping mechanisms (eg, CTLA-4, CD39, IL-10, IL-35, TGF-ß, granzyme B). TIM3+ cells emerge as a potentially highly suppressive population. © 2020 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.