HIF-1α accumulation upregulates MICA and MICB expression on human cardiomyocytes and enhances NK cell cytotoxicity during hypoxia-reoxygenation

Association of MICA and AT1R antibodies with antibody-mediated rejection and cardiac allograft vasculopathy in a pediatric heart transplant recipient

BACKGROUND

Recipient antibodies against mismatched donor-specific human leukocyte antigens (HLA) are known to be associated with antibody-mediated rejection (AMR), posing increased risks of cardiac allograft vasculopathy (CAV), graft dysfunction, and graft loss after heart transplant (HTx). However, the impact of non-HLA antibodies on HTx outcome is not yet well defined.

CASE DESCRIPTION

Here we report a case of a pediatric patient, who was retransplanted after developing CAV in his first heart allograft. Five years post 2nd HTx, the patient presented with graft dysfunction and mild rejection (ACR 1R, AMR 1H, C4d Neg) in the cardiac biopsy in the absence of HLA donor-specific antibodies (DSAs). We detected strong antibodies against non-HLA antigens, including angiotensin II receptor type 1 (AT1R) and donor-specific MHC class I chain-related gene A (MICA), in the patient's serum that were implicated in the AMR and accelerated CAV of his second allograft, and likely played a role in the loss of his first allograft as well.

CONCLUSION

This case report underscores the clinical relevance of non-HLA antibodies in heart transplantation and highlights the value of incorporating these tests in the immunological risk assessment and post-transplant monitoring of HTx recipients.

Emerging role of hypoxia-inducible factor-1α in inflammatory autoimmune diseases: A comprehensive review

Hypoxia-inducible factor-1α (HIF-1α) is a primary metabolic sensor, and is expressed in different immune cells, such as macrophage, dendritic cell, neutrophil, T cell, and non-immune cells, for instance, synovial fibroblast, and islet β cell. HIF-1α signaling regulates cellular metabolism, triggering the release of inflammatory cytokines and inflammatory cells proliferation. It is known that microenvironment hypoxia, vascular proliferation, and impaired immunological balance are present in autoimmune diseases. To date, HIF-1α is recognized to be overexpressed in several inflammatory autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis, and function of HIF-1α is dysregulated in these diseases. In this review, we narrate the signaling pathway of HIF-1α and the possible immunopathological roles of HIF-1α in autoimmune diseases. The collected information will provide a theoretical basis for the familiarization and development of new clinical trials and treatment based on HIF-1α and inflammatory autoimmune disorders in the future.

When a Friend Becomes Your Enemy: Natural Killer Cells in Atherosclerosis and Atherosclerosis-Associated Risk Factors

Atherosclerosis (ATS), the change in structure and function of arteries with associated lesion formation and altered blood flow, is the leading cause of cardiovascular disease, the number one killer worldwide. Beyond dyslipidemia, chronic inflammation, together with aberrant phenotype and function of cells of both the innate and adaptive immune system, are now recognized as relevant contributors to atherosclerosis onset and progression. While the role of macrophages and T cells in atherosclerosis has been addressed in several studies, Natural Killer cells (NKs) represent a poorly explored immune cell type, that deserves attention, due to NKs’ emerging contribution to vascular homeostasis. Furthermore, the possibility to re-polarize the immune system has emerged as a relevant tool to design new therapies, with some succesfull exmples in the field of cancer immunotherapy. Thus, a deeper knowledge of NK cell pathophysiology in the context of atherosclerosis and atherosclerosis-associated risk factors could help developing new preventive and treatment strategies, and decipher the complex scenario/history from “the risk factors for atherosclerosis” Here, we review the current knowledge about NK cell phenotype and activities in atherosclerosis and selected atherosclerosis risk factors, namely type-2 diabetes and obesity, and discuss the related NK-cell oriented environmental signals.

NK cells sense tumors, course of disease and treatments: Consequences for NK-based therapies

The recent findings on NK activation indicate that these cells are important antitumor effectors. NK cells participate in the graft-vs.-leukemia effect to control the relapse in leukemic patients transplanted with allogeneic hematopoietic stem cells. In various tumors, correlation between NK cell infiltrates and prognosis were reported. However, tumor-infiltrating NK cells are yet poorly characterized. We here summarize our results and the recent studies of the literature on tumor-infiltrating NK cells, and discuss the impact of these novel insights into NK cell responses against tumors for the design of NK cell-based therapies.

Origin and Consequences of Necroinflammation

When cells undergo necrotic cell death in either physiological or pathophysiological settings in vivo, they release highly immunogenic intracellular molecules and organelles into the interstitium and thereby represent the strongest known trigger of the immune system. With our increasing understanding of necrosis as a regulated and genetically determined process (RN, regulated necrosis), necrosis and necroinflammation can be pharmacologically prevented. This review discusses our current knowledge about signaling pathways of necrotic cell death as the origin of necroinflammation. Multiple pathways of RN such as necroptosis, ferroptosis, and pyroptosis have been evolutionary conserved most likely because of their differences in immunogenicity. As the consequence of necrosis, however, all necrotic cells release damage associated molecular patterns (DAMPs) that have been extensively investigated over the last two decades. Analysis of necroinflammation allows characterizing specific signatures for each particular pathway of cell death. While all RN-pathways share the release of DAMPs in general, most of them actively regulate the immune system by the additional expression and/or maturation of either pro- or anti-inflammatory cytokines/chemokines. In addition, DAMPs have been demonstrated to modulate the process of regeneration. For the purpose of better understanding of necroinflammation, we introduce a novel classification of DAMPs in this review to help detect the relative contribution of each RN-pathway to certain physiological and pathophysiological conditions.

Aleglitazar, a dual peroxisome proliferator-activated receptor-α and -γ agonist, protects cardiomyocytes against the adverse effects of hyperglycaemia

PURPOSE

To assess the effects of Aleglitazar on hyperglycaemia-induced apoptosis.

METHODS

We incubated human cardiomyocytes, cardiomyocytes from cardiac-specific peroxisome proliferator-activated receptor-γ knockout or wild-type mice in normoglycaemic or hyperglycaemic conditions (glucose 25 mM). Cells were treated with different concentrations of Aleglitazar for 48 h. We measured viability, apoptosis, caspase-3 activity, cytochrome-C release, total antioxidant capacity and reactive oxygen species formation in the treated cardiomyocytes. Human cardiomyocytes were transfected with short interfering RNA against peroxisome proliferator-activated receptor-α or peroxisome proliferator-activated receptor-γ.

RESULTS

Aleglitazar attenuated hyperglycaemia-induced apoptosis, caspase-3 activity and cytochrome-C release and increased viability in human cardiomyocyte, cardiomyocytes from cardiac-specific peroxisome proliferator-activated receptor-γ knockout and wild-type mice. Hyperglycaemia reduced the antioxidant capacity and Aleglitazar significantly blunted this effect. Hyperglycaemia-induced reactive oxygen species production was attenuated by Aleglitazar in both human cardiomyocyte and wild-type mice cardiomyocytes. Aleglitazar improved cell viability in cells exposed to hyperglycaemia. The protective effect was partially blocked by short interfering RNA against peroxisome proliferator-activated receptor-α alone and short interfering RNA against peroxisome proliferator-activated receptor-γ alone and completely blocked by short interfering RNA to both peroxisome proliferator-activated receptor-α and peroxisome proliferator-activated receptor-γ.

CONCLUSION

Aleglitazar protects cardiomyocytes against hyperglycaemia-induced apoptosis by combined activation of both peroxisome proliferator-activated receptor-α and peroxisome proliferator-activated receptor-γ in a short-term vitro model.

Aleglitazar, a Balanced Dual PPARα and -γ Agonist, Protects the Heart Against Ischemia-Reperfusion Injury

PURPOSE

To evaluate whether aleglitazar (Ale), a dual PPARα/γ agonist, has additive effects on myocardial protection against ischemia-reperfusion injury.

METHODS

Human cardiomyocytes (HCMs), cardiomyocytes from cardiac-specific PPARγ knockout (MCM-PPARγ (CKO) ) or wild type (MCM-WT) mice were incubated with different concentrations of Ale, and subjected to simulated ischemia-reperfusion (SIR) or normoxic conditions (NSIR). Cell viability, apoptosis and caspase-3 activity were determined. HCMs were transfected with siRNA against PPARα (siPPARα) or PPARγ (siPPARγ) followed by incubation with Ale. PPARα/γ DNA binding capacity was measured. Cell viability, apoptosis and levels of P-AKT and P-eNOS were assessed. Infarct size following 30 min coronary artery occlusion and 24 h reperfusion were assessed in WT and db/db diabetic mice following 3-day pretreatment with vehicle, Ale or glimeperide.

RESULTS

Ale (at concentrations of 150-600 nM) increased cell viability and reduced apoptosis in HCMs, MCM-WT and MCM-PPAR (CKO) exposed to SIR. In HCM, the protective effect was partially blocked by siPPARα alone or siPPARγ alone, and completely blocked by siPPARα+siPPARγ. Ale increased P-Akt/P-eNOS in HCMs. P-Akt or P-eNOS levels were decreased when PPARα alone, PPARγ alone and especially when both were knocked down. Peritoneal GTTs revealed that db/db mice had developed impaired glucose tolerance and insulin sensitivity, which were normalized by Ale or glimepiride treatment. Ale, but not glimepiride, limited infarct size in both WT and diabetic mice after ischemia-reperfusion.

CONCLUSIONS

Ale protects against myocardial apoptosis caused by hypoxia-reoxygenation in vitro and reduces infarct size in vivo.

Transplantation and Damage-Associated Molecular Patterns (DAMPs)

Upon solid organ transplantation and during cancer immunotherapy, cellular stress responses result in the release of damage-associated molecular patterns (DAMPs). The various cellular stresses have been characterized in detail over the last decades, but a unifying classification based on clinically important aspects is lacking. Here, we provide an in-depth review of the most recent literature along with a unifying concept of the danger/injury model, suggest a classification of DAMPs, and review the recently elaborated mechanisms that result in the emission of such factors. We further point out the differences in DAMP responses including the release following a heat shock pattern, endoplasmic reticulum stress, DNA damage-mediated DAMP release, and discuss the diverse pathways of regulated necrosis in this respect. The understanding of various forms of DAMPs and the consequences of their different release patterns are prerequisite to associate serum markers of cellular stresses with clinical outcomes.

Tissue-Resident NK Cells Mediate Ischemic Kidney Injury and Are Not Depleted by Anti-Asialo-GM1 Antibody

NK cells are innate lymphoid cells important for immune surveillance, identifying and responding to stress, infection, and/or transformation. Whereas conventional NK (cNK) cells circulate systemically, many NK cells reside in tissues where they appear to be poised to locally regulate tissue function. In the present study, we tested the contribution of tissue-resident NK (trNK) cells to tissue homeostasis by studying ischemic injury in the mouse kidney. Parabiosis experiments demonstrate that the kidney contains a significant fraction of trNK cells under homeostatic conditions. Kidney trNK cells developed independent of NFIL3 and T-bet, and they expressed a distinct cell surface phenotype as compared with cNK cells. Among these, trNK cells had reduced asialo-GM1 (AsGM1) expression relative to cNK cells, a phenotype observed in trNK cells across multiple organs and mouse strains. Strikingly, anti-AsGM1 Ab treatment, commonly used as an NK cell-depleting regimen, resulted in a robust and selective depletion of cNKs, leaving trNKs largely intact. Using this differential depletion, we tested the relative contribution of cNK and trNK cells in ischemic kidney injury. Whereas anti-NK1.1 Ab effectively depleted both trNK and cNK cells and protected against ischemic/reperfusion injury, anti-AsGM1 Ab preferentially depleted cNK cells and failed to protect against injury. These data demonstrate unanticipated specificity of anti-AsGM1 Ab depletion on NK cell subsets and reveal a new approach to study the contributions of cNK and trNK cells in vivo. In total, these data demonstrate that trNK cells play a key role in modulating local responses to ischemic tissue injury in the kidney and potentially other organs.

A hypoxia-induced decrease of either MICA/B or Hsp70 on the membrane of tumor cells mediates immune escape from NK cells

Recent findings suggest that hypoxia of the tumor microenvironment contributes to immune escape from natural killer (NK) cell-mediated cytotoxicity. Heat shock protein 70 (Hsp70) and the stress-regulated major histocompatibility class I chain-related protein A and B (MICA/B) both serve as ligands for activated NK cells when expressed on the cell surface of tumor cells. Herein, we studied the effects of hypoxia and hypoxia-inducible factor-1α (HIF-1α) on the membrane expression of these NK cell ligands in H1339 with high and MDA-MB-231 tumor cells with low basal HIF-1α levels and its consequences on NK cell-mediated cytotoxicity. We could show that a hypoxia-induced decrease in the membrane expression of MICA/B and Hsp70 on H1339 and MDA-MB-231 cells, respectively, is associated with a reduced sensitivity to NK cell-mediated lysis. A knockdown of HIF-1α revealed that the decreased surface expression of MICA/B under hypoxia is dependent on HIF-1α in H1339 cells with high basal HIF-1α levels. Hypoxia and HIF-1α did not affect the MICA/B expression in MDA-MB-231 cells but reduced the Hsp70 membrane expression which in turn also impaired NK cell recognition. Furthermore, we could show that the hypoxia-induced decrease in membrane Hsp70 is independent of HIF-1α in MDA-MB-231. Our data indicate that hypoxia-induced downregulation of both NK cell ligands MICA/B and Hsp70 impairs NK cell-mediated cytotoxicity, whereby only MICA/B appears to be regulated by HIF-1α.

HIF-1α regulated tongue squamous cell carcinoma cell growth via regulating VEGF expression in a xenograft model

OBJECTIVE

We aimed to study the mechanism of hypoxia-inducible factor 1 alpha (HIF-1α) regulating the cell proliferation of tongue squamous cell carcinoma (TSCC) via vascular endothelial growth factor (VEGF).

METHODS

We used RNA interference (RNAi) technique, transfected chemically synthesized siRNA against HIF-1α into CAL-27 cells, and detected the expression of HIF-1α and VEGF by real time-PCR and Western blotting in order to find out if HIF-1α regulated the expression of VEGF. A xenograft experiment was carried out to observe the role of HIF-1α on the tumor growth of tongue squamous cell carcinoma.

RESULTS

HIF-1α and VEGF mRNA expression was significantly downregulated 36 and 48 h after transfection (P<0.05); the protein expression of HIF-1α and VEGF was also significantly suppressed by siRNA against HIF-1α. Furthermore, intratumoraly injection of HIF-1α targeting siRNA suppressed tumor growth in nude mice.

CONCLUSIONS

HIF-1α regulated VEGF expression, and they may contribute to TSCC cell tumor growth.

Dickkopf-1 (DKK1) phosphatase and tensin homolog on chromosome 10 (PTEN) crosstalk via microRNA interference in the diabetic heart

Competitive endogenous RNAs (ceRNAs) regulate mRNA transcripts containing common microRNA (miRNA) recognition elements (MREs) through sequestration of shared miRNAs. Interactions of ceRNA have been demonstrated in cancerous cells. However, a paucity of information is available relative to the interactions of ceRNAs interaction in diabetes mellitus and the myocardium. The purpose of this study is to assess the potential role of DKK1 and PTEN in ceRNA regulation utilizing their common miRNAs in diabetic cardiomyocytes. The interactions' regulation between PTEN and DKK1 were determined in two diabetic models in vivo (streptozotocin-induced type-1 DM mice and db/db mice) and in vitro (human cardiomyocytes cells exposed to hyperglycemia). The levels of DKK1 and PTEN (mRNA and protein) were upregulated in parallel in all three diabetic models. DKK1 modulates PTEN protein levels in a miRNA and 3'UTR-dependent manner. RNAi-mediated DKK1 gene silencing resulted in a decreased PTEN expression and vice versa. The effect was blocked when Dicer was inhibited. Silencing either PTEN or DKK1 resulted in an increase of the availabilities of shared miRNAs. The silencing of either PTEN or DKKI resulted in a suppression end of the luciferase-PTEN 3'UTR activity. However, the over expression of DKK1 3'UTR or PTEN 3'UTR resulted in an increase in the activity. The attenuation of DKK1 increased AKT phosphorylation, improved glucose uptake and decreased apoptosis in HCMs exposed to hyperglycemia. The effects were blocked by PI3K inhibition. DKK1 and PTEN transcripts are co-upregulated in DM and hyperglycemia. DKK1 and PTEN serve as ceRNA, affecting the expression of each other via competition for miRNAs binding.

Hypoxia downregulates the expression of cell surface MICA without increasing soluble MICA in osteosarcoma cells in a HIF-1α-dependent manner

Tumor cells express NKG2D ligands on their cell surface, which are the ligands of the activating receptor, NKG2D, that is expressed on the surface of NK cells. The binding of NK cells to tumor cells through the interaction of NKG2D and its ligands induces the cytolysis of the tumor cells. In the present study, we investigated the effects of hypoxia on the expression of NKG2D ligands on the surface of human osteosarcoma cells using three cell lines. To produce hypoxic and normoxic conditions, the osteosarcoma cell lines were cultured under 1 and 20% O2 conditions, respectively. The osteosarcoma cells expressed NKG2D ligands such as MHC class I-related chain molecules A and B (MICA and MICB) and the UL16-binding proteins 1, 2 and 3 (ULBP 1, 2 and 3). MICA was the most frequently expressed NKG2D ligand in the osteosarcoma cells. Hypoxia decreased the expression of cell surface MICA only without increasing the secretion of soluble MICA, which is produced by proteolytic cleavage of cell surface MICA. Hypoxia consistently decreased the susceptibility of the osteosarcoma cells to the cytotoxicity of the NK cells. Hypoxia induced the expression of hypoxia-inducible factor-1α (HIF-1α), and knockdown of the expression of HIF-1α using small interfering RNA increased the expression of cell surface MICA and concomitantly increased the level of soluble MICA. Hypoxia decreased the production of nitric oxide (NO) metabolites (nitrite and nitrate), thus, indicating a decreasing effect on NO production. However, a NO donor, NOC18, decreased the expression of cell surface MICA without any apparent effects on the expression of HIF-1α under both hypoxic and normoxic conditions. The present results indicate that hypoxia downregulates the expression of cell surface MICA without increasing the level of soluble MICA in a HIF-1α-dependent manner and suggest that the effects of hypoxia are not linked to the hypoxia-induced reduction of NO production.

Differential expression of microRNAs during allograft rejection

MicrorRNA are small noncoding RNA molecules that regulate the posttranscriptional expression of target genes. In addition to being involved in many biologic processes, microRNAs are important regulators in innate and adaptive immune responses. Distinct sets of expressed microRNAs are found in different cell types and tissues and aberrant expression of microRNAs is associated with many disease states. MicroRNA expression was examined in a model of heterotopic heart transplantation by microarray analyses and a unique profile was detected in rejecting allogeneic transplants (BALB/c → C57BL/6) as compared to syngeneic transplants (C57BL/6 → C57BL/6). The microRNA miR-182 was significantly increased in rejecting cardiac allografts and in mononuclear cells that infiltrate the grafts. Forkhead box (FOX) proteins are a family of important transcription factors and FOXO1 is a target of miR-182. As miR-182 increases after transplant, there is a concomitant posttranscriptional decrease in FOXO1 expression in heart allografts that is localized to both the cardiomyocytes and CD3(+) T cells. The microRNA miR-182 is significantly increased in both peripheral blood mononuclear cells and plasma during graft rejection suggesting potential as a biomarker of graft status. Our results identify microRNAs that may regulate alloimmune responses and graft outcomes.

Protective effects of ulinastatin on pulmonary damage in rats following scald injury

Organ protection is desirable in severe burn/scald injuries, and damage mechanisms and thus effective therapies following scald injury have not been fully elucidated. Our aim was to examine the beneficial effects of ulinastatin on pulmonary damage associated with scald injury. Lewis rats were subjected to 30% total body surface area (TBSA) scald injury and were randomly divided into a burn control (S group) and an ulinastatin-treated group (U group). Lung malondialdehyde (MDA) and superoxide dismutase (SOD) levels were determined, and the lungs were examined histologically with immunohistochemistry (IHC) as well for the major histocompatibility complex (MHC) class I chain-related antigen A (MICA) and Bcl-2 at 24, 48 and 72 h after the injury. The expression of spleen human leucocyte antigen-DR (HLA-DR) was detected by immunohistochemistry analysis. Selectins and adhesion molecules in lungs and serum were also detected. The lung injury degree was represented as wet/dry (W/D) values and alveolar thickness. Ulinastatin decreased MDA levels and ameliorated the down-regulation of SOD activity. MICA was up-regulated after the scald, and this up-regulation was greatly diminished by ulinastatin. Bcl-2 was up-regulated after the scald, especially in the U group. The spleen HLA-DR expression demonstrated the immunoregulatory effects of ulinastatin, which effectively protected the pulmonary tissues from scald-induced injury. Our results demonstrated that pulmonary damage was associated with autoimmunity and oxidant attack after severe scald. Ulinastatin exhibits significant protective effects on these effects.

Thyroid hormones as modulators of immune activities at the cellular level

BACKGROUND

Increasing evidence suggests that thyroid hormones, L-thyroxine (T(4)) and 3,3',5-triiodo-L-thyronine (T(3)), are modulators of the immune response. In monocytes, macrophages, leukocytes, natural killer cells, and lymphocytes, a wide range of immune functions such as chemotaxis, phagocytosis, generation of reactive oxygen species (ROS), and cytokine synthesis and release are altered under hypo- and hyperthyroid conditions.

SUMMARY

Hyperthyroidism decreases the proinflammatory activities of monocytes and macrophages, whereas enhancement of phagocytosis and increased levels of ROS may occur during hypothyroidism. The expression of proinflammatory molecules such as macrophage inflammatory protein-1α and interleukin-1β increases in hypothyroidism. However, in Kupffer cells, proinflammatory activities such as the respiratory burst, nitric oxide synthase activity, and tumor necrosis factor-α expression may result from increased T(3) levels. Thyroid hormones also affect natural killer cell activity and cell-mediated immune responses. Still, for many immune cells no clear correlation has been found so far between abnormally high or low T(3) or T(4) levels and the effects observed on the immune responses.

CONCLUSIONS

In this review we outline the contributions of thyroid hormones to different aspects of innate and adaptive immune responses. The relationship between thyroid hormones and immune cells is complex and T(3) and T(4) may modulate immune responses through both genomic and nongenomic mechanisms. Future studies of the molecular signaling mechanisms involved in this cross-talk between thyroid hormones and the immune system may support development of new strategies to improve clinical immune responses.

NKG2D and its ligands: active factors in the outcome of solid organ transplantation?

The role of natural killer (NK) cells in solid organ transplantation is not well established, although several recent reports highlight the importance of the activating receptor NKG2D and its ligands in the development of rejection during transplantation. The human NKG2D ligands (MICA and MICB) are induced in allografts during acute and chronic rejection, and the presence of anti-MICA antibodies is correlated with a higher incidence of rejection. The binding of these ligands to its receptor NKG2D activates NK cells, enhances the functions of effectors, and allows NK cells to function as a bridge between innate and adaptive immunity associated with the transplantation. In fact, blockage of NKG2D with the anti-NKG2D monoclonal antibodies prolongs graft survival and prevents CD28-independent rejection in heart and skin allograft mouse models. Furthermore, the current immunosuppressive therapies can modulate the expression of NK cell receptors and consequently the effector functions of NK cells. That is particularly important during the first few months after transplantation, when the susceptibility to opportunistic viral infections is higher and NKG2D has an essential role. In this review, we analyze in detail the potential role of the NKG2D-activating receptor and its ligands in the immune responses during the outcome of solid organ transplantation. These findings open a new pathway for therapeutic intervention that can contribute to tolerance in solid organ transplantation.

The effect of MICA antigens on transplant outcomes: a systematic review

BACKGROUND AND OBJECTIVE

Human major histocompatibility complex class I-related gene A (MICA) is reportedly associated with poor transplant outcomes and a high risk of acute and chronic rejection in solid organ transplantation. However, studies on these risks have found conflicting results. In order to identify areas in which additional research is needed, we have undertaken the first systematic review of evidence concerning the risk of anti-MICA antibodies in recipients' sera.

METHODS

We searched MEDLINE, EMBASE, and the Cochrane Library for original reports of clinical studies involving detection of MICA abs in transplant recipients' sera which used survival rate, acute rejection, and/or chronic rejection as outcome measures. RevMan 5.0.15 was used to calculate relative risk (RR), odds ratios (ORs), and 95% confidence intervals (95%CIs).

RESULTS

We found 18 relevant articles, with a total of 6,607 recipients. Follow-up duration ranged from 1 to 15 years. In studies with more than 2 years of follow-up, anti-MICA abs positive in kidney recipients' post-transplant sera was associated with a lower graft survival rate (4 years: RR = 2.04, 95%CI 1.30 to 3.22; 3 years: OR = 3.56, 95%CI 1.47 to 8.62; 2 years: RR = 2.17, 95%CI 1.09 to 4.31) and a higher acute rejection rate (RR = 1.92, 95%CI 1.27 to 2.91), but there was no clear association with chronic rejection. Similar conclusions could not be drawn for heart or liver transplantation due to possible confounding by anti-HLA abs and the small sample sizes of the available studies.

CONCLUSION

Anti-MICA antibodies in recipients' sera may associated with poor graft survival rates and high risk of acute and chronic rejection in solid organ transplantation, but more rigorous studies are needed to confirm or refute this relationship. Current immunosuppressive therapy may fail to suppress the harmful effect of MICA antigens.