Pharmacokinetics and Pharmacodynamics of T-Cell Bispecifics in the Tumour Interstitial Fluid

The goal of this study is to investigate the pharmacokinetics in plasma and tumour interstitial fluid of two T-cell bispecifics (TCBs) with different binding affinities to the tumour target and to assess the subsequent cytokine release in a tumour-bearing humanised mouse model. Pharmacokinetics (PK) as well as cytokine data were collected in humanised mice after iv injection of cibisatamab and CEACAM5-TCB which are binding with different binding affinities to the tumour antigen carcinoembryonic antigen (CEA). The PK data were modelled and coupled to a previously published physiologically based PK model. Corresponding cytokine release profiles were compared to in vitro data. The PK model provided a good fit to the data and precise estimation of key PK parameters. High tumour interstitial concentrations were observed for both TCBs, influenced by their respective target binding affinities. In conclusion, we developed a tailored experimental method to measure PK and cytokine release in plasma and at the site of drug action, namely in the tumour. Integrating those data into a mathematical model enabled to investigate the impact of target affinity on tumour accumulation and can have implications for the PKPD assessment of the therapeutic antibodies.

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Keratinocytes Regulate the Threshold of Inflammation by Inhibiting T Cell Effector Functions

Cells ◽

10.3390/cells10071606 ◽

2021 ◽

Vol 10 (7) ◽

pp. 1606

Author(s):

Peter Seiringer ◽

Stefanie Eyerich ◽

Kilian Eyerich ◽

Daniela Dittlein ◽

Anna Caroline Pilz ◽

...

Keyword(s):

Cell Proliferation ◽

T Cell ◽

Cytokine Production ◽

Nickel Sulfate ◽

Human Keratinocytes ◽

T Cell Proliferation ◽

Effector Functions ◽

The Impact ◽

Cell Effector

Whilst the importance of keratinocytes as a first-line defense has been widely investigated, little is known about their interactions with non-resident immune cells. In this study, the impact of human keratinocytes on T cell effector functions was analyzed in an antigen-specific in vitro model of allergic contact dermatitis (ACD) to nickel sulfate. Keratinocytes partially inhibited T cell proliferation and cytokine production. This effect was dependent on the keratinocyte/T cell ratio and was partially reversible by increasing the number of autologous dendritic cells. The inhibition of T cell proliferation by keratinocytes was independent of the T cell subtype and antigen presentation by different professional antigen-presenting cells. Autologous and heterologous keratinocytes showed comparable effects, while the fixation of keratinocytes with paraformaldehyde abrogated the immunosuppressive effect. The separation of keratinocytes and T cells by a transwell chamber, as well as a cell-free keratinocyte supernatant, inhibited T cell effector functions to the same amount as directly co-cultured keratinocytes, thus proving that soluble factor/s account for the observed suppressive effects. In conclusion, keratinocytes critically control the threshold of inflammatory processes in the skin by inhibiting T cell proliferation and cytokine production.

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Interferon resistance of cutaneous T-cell lymphoma–derived clonal T-helper 2 cells allows selective viral replication

Blood ◽

10.1182/blood.v97.2.523 ◽

2001 ◽

Vol 97 (2) ◽

pp. 523-527 ◽

Cited By ~ 25

Author(s):

Reinhard Dummer ◽

Udo Döbbeling ◽

Ralf Geertsen ◽

Jörg Willers ◽

Günter Burg ◽

...

Keyword(s):

T Cell ◽

Viral Replication ◽

Human Leukocyte ◽

T Helper ◽

Cd4 Cells ◽

Efficient Treatment ◽

T Helper 2 ◽

Ifn Γ ◽

The Impact

Abstract Cutaneous T-cell lymphomas (CTCL) comprise a heterogeneous group of lymphoproliferative disorders that are characterized by an accumulation of T-lymphocytes in the skin and occasionally in blood known as Sézary syndrome (SS). In most cases the dominant clone displays T-helper 2 cytokines. Because IFN-γ is a natural inhibitor of T-helper 2 cells and IFN-α is frequently used in CTCL, the impact of IFNs on SS-derived purified clonal T-helper 2 cells was studied using anti-Vβ antibodies. Moreover, IFNs are known to mediate virus resistance in normal cells. The isolated clonal CD4+ cells, but not the nonclonal CD4+ cells, appeared resistant to IFN-γ and IFN-α stimulation in terms of human leukocyte antigen up-regulation and MxA induction caused in part by alterations in Stat-1 molecule mRNA and IFNγR1 mRNA transcription. The IFN resistance of the patient-derived clonal cells was then targeted by vesicular stomatitis virus infection after IFN-α priming, resulting in selective viral replication in clonal cells. In contrast, nonclonal cells of the same patient showed IFN-dependent MxA expression, which is a major mediator protein of viral protection. The IFN resistance of the dominant T-helper 2 cells might be important for lymphomagenesis. Interferon signaling deficiencies can be targeted for purging patients' cells in vitro. Furthermore, this approach may allow specific molecular interventions, resulting in the efficient treatment of CTCL and other IFN-resistant neoplasms such as lung cancer.

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CD18 Antibody Application Blocks Unwanted Off-Target T Cell Activation Caused by Bispecific Antibodies

Cancers ◽

10.3390/cancers13184596 ◽

2021 ◽

Vol 13 (18) ◽

pp. 4596

Author(s):

Joseph Kauer ◽

Fabian Vogt ◽

Ilona Hagelstein ◽

Sebastian Hörner ◽

Melanie Märklin ◽

...

Keyword(s):

T Cell ◽

T Cell Activation ◽

Cell Activation ◽

Lymphoid Cells ◽

Bispecific Antibodies ◽

Target Cells ◽

Cytokine Release ◽

Life Threatening ◽

Blocking Antibodies

T cell-recruiting bispecific antibodies (bsAbs) are successfully used for the treatment of cancer. However, effective treatment with bsAbs is so far hampered by severe side effects, i.e., potentially life-threatening cytokine release syndrome. Off-target T cell activation due to binding of bispecific CD3 antibodies to T cells in the absence of target cells may contribute to excessive cytokine release. We report here, in an in vitro setting, that off-target T cell activation is induced by bsAbs with high CD3 binding affinity and increased by endothelial- or lymphoid cells that act as stimulating bystander cells. Blocking antibodies directed against the adhesion molecules CD18/CD54 or CD2/CD58 markedly reduced this type of off-target T cell activation. CD18 blockade—in contrast to CD2—did not affect the therapeutic activity of various bsAbs. Since CD18 antibodies have been shown to be safely applicable in patients, blockade of this integrin holds promise as a potential target for the prevention of unwanted off-target T cell activation and allows the application of truly effective bsAb doses.

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663 Media based on the metabolic composition of tumor interstitial fluid reveals persistent T cell dysfunction induced through arginine deprivation and exposure to the oncometabolite phosphoethanolamine

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2021-sitc2021.663 ◽

2021 ◽

Vol 9 (Suppl 3) ◽

pp. A691-A691

Author(s):

Yupeng Wang ◽

Chufan Cai ◽

Dayana Rivadeneira ◽

Alexander Muir ◽

Greg Delgoffe

Keyword(s):

T Cells ◽

T Cell ◽

Cd8 T Cells ◽

Interstitial Fluid ◽

Cytokine Production ◽

Cell Dysfunction ◽

Kennedy Pathway ◽

T Cell Dysfunction ◽

Tumor Interstitial Fluid

BackgroundWhile CD8 T cells are crucial for anti-tumor immunity, tumor infiltrating CD8 T cells encounter stressors which deviate their differentiation to a dysfunctional, exhausted phenotype. T cell functions are closely regulated by T cell metabolism, and the dysfunctional vasculature in tumor tissues and the deregulated metabolism of tumor cells lead to depletion of nutrients and accumulation of metabolic wastes in the tumor microenvironment (TME). Thus, the unbalanced levels of the nutrients and the metabolic wastes might skew the metabolism of T cells thus contributing to T cell dysfunction.MethodsOvalbumin-specific OT-I cells were activated with SIINFEKL/IL2 and cultured with IL2. The tumor interstitial fluid media (TIFM) was formulated based on the concentrations of the metabolites measured in the tumor interstitial fluid of pancreatic ductal adenocarcinoma.1 Purified arginine and phosphoethanolamine (PEtn) were used to change their levels in TIFM/RPMI1640 culture. Expression level of cytokines and PD-1 was measured by flow cytometry.ResultsWe sought to determine how T cells would differentiate, in vitro, if they were exposed only to the metabolites present in the TME. Using media formulated to model the metabolic composition of tumor interstitial fluid (TIFM),1 we show that CD8 T cells develop features of exhausted T cells in the TIFM culture: reduced proliferation, increased expression of PD-1 and decreased cytokine production. Using 'dropout' and 'add-back' approaches, we found arginine levels as a major contributor to the proliferation defect observed in TIFM-cultured T cells. Arginine was sufficient to restore proliferative capacity to T cells cultured in TIFM, but had no effect on the inhibited cytokine production. We then asked which metabolites were enriched in the TIFM, finding that PEtn, an intermediate in the ethanolamine branch of the Kennedy pathway and an oncometabolite enriched in the interstitial of many solid tumors, up-regulates PD-1 expression and compromises the cytokine production of the cells in culture. Depletion of Pcyt2, the metabolizing enzyme of PEtn and the rate limiting enzyme in the Kennedy pathway, makes CD8 T cells resistant to the effects of PEtn.ConclusionsOur data shows that the metabolic environment in the TME can be recapitulated in vitro and is sufficient to drive T cell dysfunction. Arginine depletion acts as a major inhibitor of T cell proliferation in the TME, but the oncometabolite PEtn drives a hypofunctional effector fate of T cells. Targeting PEtn metabolism via Pcyt2 depletion or inhibition is a potential target to reinvigorate T cells and enhance anti-tumor immunity.ReferenceSullivan MR, Danai LV, Lewis CA, Chan SH, Gui DY, Kunchok T, Dennstedt EA, Vander Heiden MG, Muir A. Quantification of microenvironmental metabolites in murine cancers reveals determinants of tumor nutrient availability. Elife 2019;;8:e44235. doi: 10.7554/eLife.44235. PMID: 30990168; PMCID: PMC6510537.

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Impact of Different T Cell Depletion Protocols on Immune Reconstitution Following Allogeneic Hematopoietic Stem Cell Transplantation

Blood ◽

10.1182/blood-2020-139208 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 43-44

Author(s):

Amandine Pradier ◽

Adrien Petitpas ◽

Anne-Claire Mamez ◽

Federica Giannotti ◽

Sarah Morin ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Immune Reconstitution ◽

Cell Depletion ◽

Unrelated Donor ◽

T Cell Depletion ◽

Hematopoietic Stem ◽

Post Transplant ◽

The Impact

Introduction Allogeneic hematopoietic stem cell transplantation (HSCT) is a well-established therapeutic modality for a variety of hematological malignancies and congenital disorders. One of the major complications of the procedure is graft-versus-host-disease (GVHD) initiated by T cells co-administered with the graft. Removal of donor T cells from the graft is a widely employed and effective strategy to prevent GVHD, although its impact on post-transplant immune reconstitution might significantly affect anti-tumor and anti-infectious responses. Several approaches of T cell depletion (TCD) exist, including in vivo depletion using anti-thymocyte globulin (ATG) and/or post-transplant cyclophosphamide (PTCy) as well as in vitro manipulation of the graft. In this work, we analyzed the impact of different T cell depletion strategies on immune reconstitution after allogeneic HSCT. Methods We retrospectively analysed data from 168 patients transplanted between 2015 and 2019 at Geneva University Hospitals. In our center, several methods for TCD are being used, alone or in combination: 1) In vivo T cell depletion using ATG (ATG-Thymoglobulin 7.5 mg/kg or ATG-Fresenius 25 mg/kg); 2) in vitro partial T cell depletion (pTCD) of the graft obtained through in vitro incubation with alemtuzumab (Campath [Genzyme Corporation, Cambridge, MA]), washed before infusion and administered at day 0, followed on day +1 by an add-back of unmanipulated grafts containing about 100 × 106/kg donor T cells. The procedure is followed by donor lymphocyte infusions at incremental doses starting with 1 × 106 CD3/kg at 3 months to all patients who had received pTCD grafts with RIC in the absence of GVHD; 3) post-transplant cyclophosphamide (PTCy; 50 mg/kg) on days 3 and 4 post-HSCT. Absolute counts of CD3, CD4, CD8, CD19 and NK cells measured by flow cytometry during the first year after allogeneic HSCT were analyzed. Measures obtained from patients with mixed donor chimerism or after therapeutic DLI were excluded from the analysis. Cell numbers during time were compared using mixed-effects linear models depending on the TCD. Multivariable analysis was performed taking into account the impact of clinical factors differing between patients groups (patient's age, donor type and conditioning). Results ATG was administered to 77 (46%) patients, 15 (9%) patients received a pTCD graft and 26 (15%) patients received a combination of both ATG and pTCD graft. 24 (14%) patients were treated with PTCy and 26 (15%) patients received a T replete graft. 60% of patients had a reduced intensity conditioning (RIC). 48 (29%) patients received grafts from a sibling identical donor, 94 (56%) from a matched unrelated donor, 13 (8%) from mismatched unrelated donor and 13 (8%) received haploidentical grafts. TCD protocols had no significant impact on CD3 or CD8 T cell reconstitution during the first year post-HSCT (Figure 1). Conversely, CD4 T cells recovery was affected by the ATG/pTCD combination (coefficient ± SE: -67±28, p=0.019) when compared to the T cell replete group (Figure 1). Analysis of data censored for acute or chronic GVHD requiring treatment or relapse revealed a delay of CD4 T cell reconstitution in the ATG and/or pTCD treated groups on (ATG:-79±27, p=0.004; pTCD:-100±43, p=0.022; ATG/pTCD:-110±33, p<0.001). Interestingly, pTCD alone or in combination with ATG resulted in a better reconstitution of NK cells compared to T replete group (pTCD: 152±45, p<0.001; ATG/pTCD: 94±36, p=0.009; Figure 1). A similar effect of pTCD was also observed for B cells (pTCD: 170±48, p<.001; ATG/pTCD: 127±38, p<.001). The effect of pTCD on NK was confirmed when data were censored for GVHD and relapse (pTCD: 132±60, p=0.028; ATG/pTCD: 106±47, p=0.023) while only ATG/pTCD retained a significant impact on B cells (102±49, p=0.037). The use of PTCy did not affect T, NK or B cell reconstitution when compared to the T cell replete group. Conclusion Our results indicate that all TCD protocols with the only exception of PTCy are associated with a delayed recovery of CD4 T cells whereas pTCD of the graft, alone or in combination with ATG, significantly improves NK and B cell reconstitution. Figure 1 Disclosures No relevant conflicts of interest to declare.

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Vitamin D/CD46 Crosstalk in Human T Cells in Multiple Sclerosis

Frontiers in Immunology ◽

10.3389/fimmu.2020.598727 ◽

2020 ◽

Vol 11 ◽

Author(s):

Justin Killick ◽

Joanne Hay ◽

Elena Morandi ◽

Sonja Vermeren ◽

Saniya Kari ◽

...

Keyword(s):

Multiple Sclerosis ◽

Vitamin D ◽

T Cells ◽

T Cell ◽

Chronic Inflammatory Disease ◽

Vitamin D Supplementation ◽

Type I ◽

T Cell Migration ◽

The Impact

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS), in which T-cell migration into the CNS is key for pathogenesis. Patients with MS exhibit impaired regulatory T cell populations, and both Foxp3+ Tregs and type I regulatory T cells (Tr1) are dysfunctional. MS is a multifactorial disease and vitamin D deficiency is associated with disease. Herein, we examined the impact of 1,25(OH)2D3 on CD4+ T cells coactivated by either CD28 to induce polyclonal activation or by the complement regulator CD46 to promote Tr1 differentiation. Addition of 1,25(OH)2D3 led to a differential expression of adhesion molecules on CD28- and CD46-costimulated T cells isolated from both healthy donors or from patients with MS. 1,25(OH)2D3 favored Tr1 motility though a Vitamin D-CD46 crosstalk highlighted by increased VDR expression as well as increased CYP24A1 and miR-9 in CD46-costimulated T cells. Furthermore, analysis of CD46 expression on T cells from a cohort of patients with MS supplemented by vitamin D showed a negative correlation with the levels of circulating vitamin D. Moreover, t-Distributed Stochastic Neighbor Embedding (t-SNE) analysis allowed the visualization and identification of clusters increased by vitamin D supplementation, but not by placebo, that exhibited similar adhesion phenotype to what was observed in vitro. Overall, our data show a crosstalk between vitamin D and CD46 that allows a preferential effect of Vitamin D on Tr1 cells, providing novel key insights into the role of an important modifiable environmental factor in MS.

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Modulation of the CCR5 Receptor/Ligand Axis by Seminal Plasma and the Utility of In Vitro versus In Vivo Models

Journal of Virology ◽

10.1128/jvi.00242-19 ◽

2019 ◽

Vol 93 (11) ◽

Cited By ~ 1

Author(s):

Jennifer A. Juno ◽

Kathleen M. Wragg ◽

Anne B. Kristensen ◽

Wen Shi Lee ◽

Kevin J. Selva ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Seminal Plasma ◽

Target Cells ◽

Ccr5 Expression ◽

Ccr5 Receptor ◽

The Impact ◽

Hiv 1

ABSTRACT Sexual HIV-1 transmission occurs primarily in the presence of semen. Although data from macaque studies suggest that CCR5+ CD4+ T cells are initial targets for HIV-1 infection, the impact of semen on T cell CCR5 expression and ligand production remains inconclusive. To determine if semen modulates the lymphocyte CCR5 receptor/ligand axis, primary human T cell CCR5 expression and natural killer (NK) cell anti-HIV-1 antibody-dependent beta chemokine production was assessed following seminal plasma (SP) exposure. Purified T cells produce sufficient quantities of RANTES to result in a significant decline in CCR5bright T cell frequency following 16 h of SP exposure (P = 0.03). Meanwhile, NK cells retain the capacity to produce limited amounts of MIP-1α/MIP-1β in response to anti-HIV-1 antibody-dependent stimulation (median, 9.5% MIP-1α+ and/or MIP-1β+), despite the immunosuppressive nature of SP. Although these in vitro experiments suggest that SP-induced CCR5 ligand production results in the loss of surface CCR5 expression on CD4+ T cells, the in vivo implications are unclear. We therefore vaginally exposed five pigtail macaques to SP and found that such exposure resulted in an increase in CCR5+ HIV-1 target cells in three of the animals. The in vivo data support a growing body of evidence suggesting that semen exposure recruits target cells to the vagina that are highly susceptible to HIV-1 infection, which has important implications for HIV-1 transmission and vaccine design. IMPORTANCE The majority of HIV-1 vaccine studies do not take into consideration the impact that semen exposure might have on the mucosal immune system. In this study, we demonstrate that seminal plasma (SP) exposure can alter CCR5 expression on T cells. Importantly, in vitro studies of T cells in culture cannot replicate the conditions under which immune cells might be recruited to the genital mucosa in vivo, leading to potentially erroneous conclusions about the impact of semen on mucosal HIV-1 susceptibility.

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Allergen-Induced C5a/C5aR1 Axis Activation in Pulmonary CD11b+ cDCs Promotes Pulmonary Tolerance through Downregulation of CD40

Cells ◽

10.3390/cells9020300 ◽

2020 ◽

Vol 9 (2) ◽

pp. 300 ◽

Cited By ~ 4

Author(s):

Konstantina Antoniou ◽

Fanny Ender ◽

Tillman Vollbrandt ◽

Yves Laumonnier ◽

Franziska Rathmann ◽

...

Keyword(s):

Cell Proliferation ◽

T Cells ◽

T Cell ◽

T Cell Activation ◽

Cd4 T Cells ◽

Cell Activation ◽

T Cell Proliferation ◽

C5a Receptor ◽

The Impact

Activation of the C5/C5a/C5a receptor 1 (C5aR1) axis during allergen sensitization protects from maladaptive T cell activation. To explore the underlying regulatory mechanisms, we analyzed the impact of C5aR1 activation on pulmonary CD11b+ conventional dendritic cells (cDCs) in the context of house-dust-mite (HDM) exposure. BALB/c mice were intratracheally immunized with an HDM/ovalbumin (OVA) mixture. After 24 h, we detected two CD11b+ cDC populations that could be distinguished on the basis of C5aR1 expression. C5aR1− but not C5aR1+ cDCs strongly induced T cell proliferation of OVA-reactive transgenic CD4+ T cells after re-exposure to antigen in vitro. C5aR1− cDCs expressed higher levels of MHC-II and CD40 than their C5aR1+ counterparts, which correlated directly with a higher frequency of interactions with cognate CD4+ T cells. Priming of OVA-specific T cells by C5aR1+ cDCs could be markedly increased by in vitro blockade of C5aR1 and this was associated with increased CD40 expression. Simultaneous blockade of C5aR1 and CD40L on C5aR1+ cDCs decreased T cell proliferation. Finally, pulsing with OVA-induced C5 production and its cleavage into C5a by both populations of CD11b+ cDCs. Thus, we propose a model in which allergen-induced autocrine C5a generation and subsequent C5aR1 activation in pulmonary CD11b+ cDCs promotes tolerance towards aeroallergens through downregulation of CD40.

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IMMU-46. EXAMINATION OF THE EFFECTS OF DEXAMETHASONE ON THE EFFICACY OF IMMUNOTHERAPY IN GLIOMA USING GENE-MEDIATED CYTOTOXIC IMMUNOTHERAPY

Neuro-Oncology ◽

10.1093/neuonc/noz175.538 ◽

2019 ◽

Vol 21 (Supplement_6) ◽

pp. vi129-vi129

Author(s):

Marilin Koch ◽

Mykola Zdioruk ◽

M Oskar Nowicki ◽

Estuardo Aguilar ◽

Laura Aguilar ◽

...

Keyword(s):

T Cell ◽

T Cell Activation ◽

Cell Activation ◽

Cell Function ◽

Immune Cell ◽

Symptomatic Treatment ◽

Tumor Cell Death ◽

The Impact

Abstract RATIONALE Dexamethasone is frequently used in symptomatic treatment of glioma patients, although it is known to cause immune suppression. Checkpoint inhibitor immunotherapies have not yet been successful in glioma treatments. Gene-mediated cytotoxic immunotherapy (GMCI) is an immunotherapeutic approach that uses aglatimagene besadenovec with an anti-herpetic prodrug to induce immunogenic tumor cell death and immune cell attraction to the tumor site with potent CD8 T cell activation. GMCI is currently in clinical trials for solid tumors including glioblastoma, where it showed encouraging survival results in a Phase 2 study that did not limit the use of dexamethasone. However, the effects of dexamethasone on its efficacy have not been explored. METHODS We investigated the effects of dexamethasone on GMCI in vitro using cytotoxicity and T-cell-killing assays in glioblastoma cell lines. The impact of dexamethasone in vivo was assessed in an orthotopic syngeneic murine glioblastoma model. RESULTS Cyotoxicity assays showed that Dexamethasone has a slight impact on GMCI in vitro. In contrast, we observed a highly significant effect in T-cell-functional assays in which killing was greatly impaired. Immune cell response assays revealed a reduced T-cell proliferation after co-culture with supernatant from dexamethasone or combination treated glioblastoma cells in contrast to GMCI alone. In a murine model, the combination of GMCI and dexamethasone resulted in a significant reduction in median symptom-free survival (29d) in comparison to GMCI alone (39.5d) (P = 0.0184). CONCLUSION Our data suggest that high doses of dexamethasone may negatively impact the efficacy of immunotherapy for glioma, which may be a consequence of impaired T cell function. These results support the idea that there is a need in identifying possible alternatives to dexamethasone to maximize the effectiveness of immunostimulatory therapies such as GMCI.

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Adoptive Infusion of Allogeneic KIR Ligand Mismatched NK Cells Reduce GVHD in an MHC Matched Allogeneic Stem Cell Transplantation Model.

Blood ◽

10.1182/blood.v106.11.1310.1310 ◽

2005 ◽

Vol 106 (11) ◽

pp. 1310-1310

Author(s):

Andreas Lundqvist ◽

Leigh Samsel ◽

Michael Eckhaus ◽

Ramaprasad Srinivasan ◽

Yoshiyuki Takahashi ◽

...

Keyword(s):

T Cell ◽

Nk Cells ◽

Murine Model ◽

Nk Cell ◽

Allogeneic Transplantation ◽

Allogeneic Bone ◽

Median Score ◽

The Impact

Abstract Retrospective data suggest NK cells play a role in protecting recipients from graft versus host disease (GVHD) in the setting of killer IgG-like receptor (KIR) ligand incompatibility. In humans, this protective effect is most evident with MHC mismatched transplantation, usually following in vivo or in vitro T-cell depletion. In MHC mismatched murine transplant models, lethal GVHD is reduced following the adoptive infusion of KIR ligand mismatched NK cells; it is unknown whether NK cells can mediate similar protective effects following MHC matched transplantation. Therefore, we investigated the impact of adoptively infusing KIR ligand mismatched NK cells on GVHD in an MHC matched T-cell replete murine model of allogeneic transplantation. Balb/C recipient mice underwent allogeneic bone marrow (8 x 106 cells) and splenocyte (15 x 106 cells) transplantation from B10.d2 donors following 950cGy of irradiation. Allogeneic B10.d2 donor NK cells were first isolated by negative depletion using magnetic beads selecting for CD4, CD5, CD8a, CD19, Gr-1 and Ter-119, and then expanded over 4-6 days in vitro in DMEM media containing 10% FCS and 500U/ml of IL-2. NK cell subsets (KIR ligand matched vs. KIR ligand mismatched) were then isolated by flow cytometry into Ly49I/C+ NK cells (KIR ligand mismatched in the GVHD direction for Balb/C recipients) and Ly49A/G+ NK cells (KIR ligand matched for Balb/C recipients). On day +4, recipient mice received a single tail vein injection with either KIR ligand matched, KIR ligand mismatched or unsorted “bulk” NK cells (0.5–1.0 x 106 NK cells). All (9/9) control transplant recipients (no adoptive NK cell infusion) as well as recipients of Ly49A/G (KIR ligand matched) NK cells (13/13) developed skin GVHD, in contrast to 4/7 (57%, p=0.03) recipients of bulk NK cells and only a minority (13% [1/8], p < 0.01) of animals receiving KIR ligand mismatched NK cells. Using a cumulative clinical GVHD scoring system (total score = 9), overall GVHD was decreased in recipients of KIR ligand mismatched NK cells (median score = 0 at day +45) compared to mice that received KIR ligand matched NK cells (median score = 3; p = 0.15) or no NK cells (median score = 3; p= 0.12); no significant difference in survival was observed between cohorts. This murine model provides the first in vivo evidence that adoptively infused KIR ligand mismatched allogeneic NK cells reduce GVHD following T-cell replete MHC matched allogeneic transplantation. The impact of infusing multiple doses of KIR ligand mismatched NK cells on GVHD and their ability to induce a graft-vs-tumor effect in tumor bearing Balb/c mice is currently being evaluated.

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