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IntroductionKidney transplants fail more often in Black than in non-Black (White, non-Black Hispanic, and Asian) recipients. We used the estimated physicochemical immunogenicity for polymorphic amino acids of donor/recipient HLAs to select weakly immunogenic kidney transplants for Black vs. White or non-Black patients.MethodsOPTN data for 65,040 donor/recipient pairs over a 20-year period were used to calculate the individual physicochemical immunogenicity by hydrophobic, electrostatic and amino acid mismatch scores (HMS, EMS, AMS) and graft-survival outcomes for Black vs. White or vs. non-Black recipients, using Kaplan-Meier survival and Cox regression analyses. Simulations for re-matching recipients with donors were based on race-adjusted HMS thresholds with clinically achievable allocations.ResultsThe retrospective median kidney graft survival was 12.0 years in Black vs. 18.6 years in White (6.6-year difference; p>0.001) and 18.4 years in non-Black (6.4-year difference; p>0.01) recipients. Only 0.7% of Blacks received transplants matched at HLA-A/B/DR/DQ (HMS=0) vs. 8.1% in Whites (p

We evaluated the impact of human leukocyte antigen (HLA) disparity (immunogenicity; IM) on long-term kidney allograft survival. The IM was quantified based on physicochemical properties of the polymorphic linear donor/recipient HLA amino acids (the Cambridge algorithm) as a hydrophobic, electrostatic, amino acid mismatch scores (HMS\AMS\EMS) or eplet mismatch (EpMM) load. High-resolution HLA-A/B/DRB1/DQB1 types were imputed to calculate HMS for primary/re-transplant recipients of deceased donor transplants. The multiple Cox regression showed the association of HMS with graft survival and other confounders. The HMS integer 0–10 scale showed the most survival benefit between HMS 0 and 3. The Kaplan–Meier analysis showed that: the HMS=0 group had 18.1-year median graft survival, a 5-year benefit over HMS>0 group; HMS ≤ 3.0 had 16.7-year graft survival, a 3.8-year better than HMS>3.0 group; and, HMS ≤ 7.8 had 14.3-year grafts survival, a 1.8-year improvement over HMS>7.8 group. Stratification based on EMS, AMS or EpMM produced similar results. Additionally, the importance of HLA-DR with/without -DQ IM for graft survival was shown. In our simulation of 1,000 random donor/recipient pairs, 75% with HMS>3.0 were re-matched into HMS ≤ 3.0 and the remaining 25% into HMS≥7.8: after re-matching, the 13.5 years graft survival would increase to 16.3 years. This approach matches donors to recipients with low/medium IM donors thus preventing transplants with high IM donors.

Relatively slow hematopoietic recovery after isolated bone marrow (I-BM) engraftment is probably caused by a disrupted microenvironment of stromal and stem cells. Thus, we compared the kinetics of hematopoietic recovery of lethally irradiated rats that received I-BM versus vascularized BM (V-BM). Total body irradiated (TBI; 8 Gy) Lewis (LEW; RT11) rats were either injected IV with syngeneic sex-mismatched 80 × 106 I-BM or transplanted with 80 × 106 V-BM in orthotopic hind limb grafts. Ten days later, peripheral blood (PB) and mesenteric lymph nodes (MLN) of these recipients were examined for the presence of donor-derived hematopoietic cells with a panel of monoclonal antibodies by FACS. To detect male cells in sex-mismatched female recipients, PCR was performed using male Y chromosome primers. When examined in PB and MLN, recipients transplanted with V-BM displayed significantly faster recovery of leukocytes (CD43+), monocytes (CD14+), and T cells (CD5+) in comparison with I-BM recipients. In addition, only V-BM (but not I-BM) groups contained stroma-like male-positive cells in PB and MLN. Our results suggest that V-BM transplants provided superior hematopoietic recovery in comparison to I-BM transplants. We postulated that close proximity between stromal and stem cells in V-BM is essential for efficient repopulation with progenitors of different lines of leukocytes.

Expression of intercellular adhesion molecule-1 (ICAM-1) and its ligand, leukocyte function antigen-1 (LFA-1), after pancreatic islet transplantation may affect both nonspecific and alloantigen-specific phases of graft destruction. We examined the effects of ICAM-1/LFA-1 blockade on the survival of islet allografts. Fresh C57BL/10 (H2 b ) pancreatic islets were transplanted under the renal subcapsular space (KC) or embolized into the liver after portal vein (PV) injection to C3H (H2 k ) mice. Recipients remained untreated or were treated for 7 days by IP administration of: ICAM-1 antisense phosphorothioate oligodeoxynucleotide (oligo) alone; anti-ICAM-1 (αICAM-1) monoclonal antibody (mAb) alone; αLFA-1 mAb alone; ICAM-1 oligo/αLFA mAb combination; αICAM-1 mAb/αLFA-1 mAb combination; or control oligo IP-8997 or IP-1082. In some experiments, donors were pretreated with ICAM-1 oligo. Inhibition of single ligand with 5.0 mg/kg ICAM-1 oligo (25.1 ± 10.3), 100 μg/daily αICAM-1 mAb (24.2 ± 8.0 days), or 50 μg/daily αLFA-1 mAb (42.8 ± 25.9 days) prolonged the survivals of KC islet allografts in comparison with untreated controls (11.9 ± 1.0 days; all p < 0.01). However, dual ICAM-1/LFA-1 blockade with either ICAM-1 oligo/αLFA-1 mAb (78.3 ± 16.5 days) or αICAM-1 mAb/αLFA-1 mAb (65.2 ±31.3 days) was the most effective therapy. Although pretreatment of donors with ICAM-1 oligo alone was ineffective (12.2 ± 0.8 days; NS), a combination of donor pretreatment and recipient treatment started 1 day prior to grafting with ICAM-1 oligo (39.2 ± 14.0 days) was more effective than the recipient treatment alone (24.6 ± 8.8 days). Furthermore, ICAM-1/LFA-1 blockade improved islet function as evaluated by glucose tolerance test, and decreased inflammation in comparison with untreated controls. Similar in vivo results were obtained following PV administration of islet allografts. Thus, ICAM-1/LFA-1 blockade prolongs the survival of pancreatic islet allografts and improves their early function.

These experiments investigated the immunosuppressive properties of liver tissue. Brown Norway (BN; RT1 n ) rat heart allografts survived in untreated control Wistar Furth (WFu; RTl u ) rat recipients for 6.2 ± 1.5 days, while allografts in animals that received rapamycin (RAPA) 0.0075 mg/kg/day and cyclosporine (CsA) 0.375 mg/kg/day delivered for 14 days by continuous intravenous infusion (civi) using osmotic pumps in conjunction with intrasplenic (i.s.) saline survived to 18.4 ± 1.3 days. i.s. addition of 3 M-KCl extracted BN hepatic antigen or unpurified BN hepatocytes (liver parenchymal cells—5 × 10 7 /kg), which exhibited a 4.8% class II antigen expression, and which alone failed to prolong allograft survival (MST = 6.0 ± 1.4 days), increased heart allograft survival to 25.3 ± 2.3 and 27.2 ± 1.9 days, respectively (p < 0.01). Hepatocyte purification using Dynabeads and Percoll reduced class II expression to 0.9% and increased allograft survival to 32.8 ± 1.6 days (p < 0.01). In contrast, the effect of 5 × 10 8 /kg BN erythrocytes, exhibiting only 0.1% class II expression, was much less (23.8 ± 1.9 days). Administration i.s. of BN splenocytes or nonparenchymal liver cells, demonstrated by flow cytometry to exhibit a 47.3 or 55.1% expression of class II antigen, respectively, failed to induce any significant increase in allograft survival (18.4 ± 4.6 and 19.4 ± 0.5 days, respectively). Survival of BN rat small bowel allografts was increased in Lewis (LEW; RTl 1 ) rat recipients treated with RAPA, CsA, and unfractionated BN hepatocytes from 10.2 ± 1.9 to 21.2 ± 1.5 days. Pretreatment with i.s. BN hepatocytes, 14 days prior to harvesting, reduced WFu lymphocyte responses to allogeneic stimulation with BN or ACI spleen cells by 75 and 70%, respectively. Addition of 1 × 10 5 unpurified donor-specific BN or third-party Buffalo (BUF; RTl b ) hepatocytes, but not supernatant, to the responder wells of MLCs resulted in a 61 and 40% suppression, respectively, of the WFu lymphocyte response induced by BN allogeneic stimulation. These findings suggest that while class I MHC expression has a significant role to play in exerting the immunosuppressive effects of hepatocytes, other influences more specific to liver may also prevail.

Optimal T cell activation and expansion require binding of the common gamma-chain (γc) cytokine Interleukin-2 (IL-2) to its cognate receptor that in turn engages a γc/Janus tyrosine kinase (Jak)3 signaling pathway. Because of its restricted expression by antigen-activated T cells and its obligatory role in promoting their survival and proliferation, IL-2 has been considered as a selective therapeutic target for preventing T cell mediated diseases. However, in order to further explore IL-2 targeted therapy, it is critical to precisely understand its role during early events of T cell activation. In this study, we delineate the role of IL-2 and other γc cytokines in promoting the survival of CD4 and CD8 T cells during early phases of priming. Under IL-2 inhibitory conditions (by neutralizing anti-IL-2 mAbs), the survival of activated CD8⁺ T cells was reduced, whereas CD4⁺ T cells remained much more resistant. These results correlated with reduced Bcl-2 expression, and mitochondrial membrane potential in CD8⁺ T cells in comparison to CD4⁺ T cells. However, using transwell co-culture assays we have found that CD4⁺ T cells could rescue the survival of CD8⁺ T cells even under IL-2 deprived conditions via secretion of soluble factors. A cytokine screen performed on CD8⁺ T cells cultured alone revealed that IL-21, another γc cytokine, was capable of rescuing their survival under IL-2 deprivation. Indeed, blocking the IL-21 signaling pathway along with IL-2 neutralization resulted in significantly reduced survival of both CD4⁺ and CD8⁺ T cells. Taken together, we have shown that under IL-2 deprivation conditions, IL-21 may act as the major survival factor promoting T cell immune responses. Thus, investigation of IL-2 targeted therapies may need to be revisited to consider blockade of the IL-21 signaling pathways as an adjunct to provide more effective control of T cell immune responses.

T cells play a major role in allograft rejection, which occurs after T cell activation by the engagement of several functional molecules to form an immune synapse with alloantigen presenting cells. In this study, the immune synapse was targeted using mAbs directed to the TCR beta-chain (TCRβ) and lymphocyte function-associated antigen-1 (LFA1) to induce long-term allograft survival. Evaluation of antigen-specific T cell responses was performed by adoptively transferring CFSE labeled transgenic OT-II cells into wild-type mice and providing OVA peptide by intravenous injection. Graft survival studies were performed in mice by transplanting BALB/c ear skins onto the flanks of C57BL/6 recipients. The anti-TCRβ plus anti-LFA1 mAb combination (but not either mAb alone) abrogated antigen-specific T cell responses invitro and invivo. Transient combination therapy with these agents resulted in significantly prolonged skin allograft survival in mice (51±10 days; p

Background: Clinical application of islet transplantation to treat type 1 diabetes has been limited by islet allograft destruction by both allogeneic and autoimmune diabetogenic T-cell responses. The current study aims at determining whether an anti-T-cell receptor (TCR) monoclonal antibody (mAb) has potential as a novel and potent induction immunotherapy for islet transplantation., Methods: We have investigated the therapeutic efficacy and mechanisms of action of anti-TCR therapy in four different murine models, which comprise either allo- or autoimmune responses alone or both together., Results: T-cell response to islet allografts was potently abrogated by a brief treatment with an anti-TCRβ mAb (clone H57-597), resulting in long-term survival of BALB/c islet allografts in streptozotocin-induced diabetic B6 mice. Moreover, transient anti-TCR treatment permanently prevented BALB/c skin allograft rejection on Rag1 B6 recipients that were reconstituted with Foxp3 cell-depleted B6 splenocytes, but did not impair the reconstituted cells' ability to reject the later transplanted C3H skin allografts (transplanted at 120 days after BALB/c skin grafting). Transient anti-TCR treatment was also able to completely prevent diabetes onset in NOD.SCID.γc mice that were transferred with lymphocytes from diabetic NOD mice. Next, transient anti-TCR treatment significantly prolonged the survival of transplanted BALB/c islets in overtly diabetic NOD mice, which comprise both allogeneic and autoimmune diabetogenic T-cell responses to the transplanted islets., Conclusions: Overall, anti-TCR mAb induced peripheral tolerance to specific alloantigens even in the absence of Foxp3-expressing natural regulatory T cells. These findings reveal the potential for using TCR-targeting mAbs as induction immunotherapy for islet transplantation.