MIF is a common genetic determinant of COVID-19 symptomatic infection and severity.

BACKGROUND: Genetic predisposition to coronavirus disease 2019 (COVID-19) may contribute to its morbidity and mortality. Because cytokines play an important role in multiple phases of infection, we examined whether commonly occurring, functional polymorphisms in macrophage migration inhibitory factor (MIF) are associated with COVID-19 infection or disease severity. AIM: To determine associations of common functional polymorphisms in MIF with symptomatic COVID-19 or its severity. METHODS: This retrospective case-control study utilized 1171 patients with COVID-19 from three tertiary medical centers in the USA, Hungary and Spain, together with a group of 637 pre-pandemic, healthy control subjects. Functional MIF promoter alleles (-794 CATT5-8,rs5844572), serum MIF and soluble MIF receptor levels, and available clinical characteristics were measured and correlated with COVID-19 diagnosis and hospitalization. Experimental mice genetically engineered to express human high- or low-expression MIF alleles were studied for response to coronavirus infection. RESULTS: In patients with COVID-19, there was a lower frequency of the high-expression MIF CATT7 allele when compared to healthy controls [11% vs. 19%, odds ratio (OR) 0.54 [0.41-0.72], P < 0.0001]. Among inpatients with COVID-19 (n = 805), there was a higher frequency of the MIF CATT7 allele compared to outpatients (n = 187) (12% vs. 5%, OR 2.87 [1.42-5.78], P = 0.002). Inpatients presented with higher serum MIF levels when compared to outpatients or uninfected healthy controls (87 ng/ml vs. 35 ng/ml vs. 29 ng/ml, P < 0.001, respectively). Among inpatients, circulating MIF concentrations correlated with admission ferritin (r = 0.19, P = 0.01) and maximum CRP (r = 0.16, P = 0.03) levels. Mice with a human high-expression MIF allele showed more severe disease than those with a low-expression MIF allele. CONCLUSIONS: In this multinational retrospective study of 1171 subjects with COVID-19, the commonly occurring -794 CATT7MIF allele is associated with reduced susceptibility to symptomatic SARS-CoV-2 infection but increased disease progression as assessed by hospitalization. These findings affirm the importance of the high-expression CATT7MIF allele, which occurs in 19% of the population, in different stages of COVID-19 infection.

A functional macrophage migration inhibitory factor promoter polymorphism is associated with reduced diffusing capacity.

Cigarette smoke exposure is the leading modifiable risk factor for chronic obstructive pulmonary disease (COPD); however, the clinical and pathologic consequences of chronic cigarette smoke exposure are variable among smokers. Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine implicated in the pathogenesis of COPD. Within the promoter of the MIF gene is a functional polymorphism that regulates MIF expression (-794 CATT5-8 microsatellite repeat) ( rs5844572 ). The role of this polymorphim in mediating disease susceptibility to COPD-related traits remains unknown. We performed a cross-sectional analysis of DNA samples from 641 subjects to analyze MIF-794 CATT5-8 ( rs5844572 ) polymorphism by standard methods. We generated multivariable logistic regression models to determine the risk of low expressing MIF alleles for airflow obstruction [defined by forced expiratory volume in 1 s (FEV1)/forced vital capacity ratio <0.70] and an abnormal diffusion capacity [defined by a diffusion capacity for carbon monoxide (DLCO) percent predicted <80%]. We then used generalized linear models to determine the association of MIF genotypes with FEV1 percent predicted and DLCO percent predicted. The MIF-794 CATT5 allele was associated with an abnormal diffusion capacity in two cohorts [odds ratio (OR): 9.31, 95% confidence interval (CI): 1.97-4.06; and OR: 2.21, 95% CI: 1.03-4.75]. Similarly, the MIF-794 CATT5 allele was associated with a reduced DLCO percentage predicted in these two cohorts: 63.5 vs. 70.0 ( P = 0.0023) and 60.1 vs. 65.4 ( P = 0.059). This study suggests an association between a common genetic polymorphism of an endogenous innate immune gene, MIF, with reduced DLCO, an important measurement of COPD severity.

MIF-CD74 signaling impedes microglial M1 polarization and facilitates brain tumorigenesis.

Microglial cells in the brain tumor microenvironment are associated with enhanced glioma malignancy. They persist in an immunosuppressive M2 state at the peritumoral site and promote the growth of gliomas. Here, we investigated the underlying factors contributing to the abolished immune surveillance. We show that brain tumors escape pro-inflammatory M1 conversion of microglia via CD74 activation through the secretion of the cytokine macrophage migration inhibitory factor (MIF), which results in a M2 shift of microglial cells. Interruption of this glioma-microglial interaction through an antibody-neutralizing approach or small interfering RNA (siRNA)-mediated inhibition prolongs survival time in glioma-implanted mice by reinstating the microglial pro-inflammatory M1 function. We show that MIF-CD74 signaling inhibits interferon (IFN)-γ secretion in microglia through phosphorylation of microglial ERK1/2 (extracellular signal-regulated protein kinases 1 and 2). The inhibition of MIF signaling or its receptor CD74 promotes IFN-γ release and amplifies tumor death either through pharmacological inhibition or through siRNA-mediated knockdown. The reinstated IFN-γ secretion leads both to direct inhibition of glioma growth as well as inducing a M2 to M1 shift in glioma-associated microglia. Our data reveal that interference with the MIF signaling pathway represents a viable therapeutic option for the restoration of IFN-γ-driven immune surveillance.

Macrophage migration inhibitory factor promotes eosinophil accumulation and tissue remodeling in eosinophilic esophagitis.

Macrophage migration inhibitory factor (MIF) is involved in eosinophil biology and in type 2 inflammation, contributing to allergic and helminthic diseases. We hypothesized that MIF participates in the pathogenesis of eosinophilic esophagitis (EoE), an allergic condition characterized by esophageal eosinophilic inflammation. MIF is highly expressed in esophageal mucosa of patients with EoE, compared with gastro-esophageal reflux disease and control patients, where it co-localizes predominantly with eosinophils. In vitro, recombinant MIF promotes human eosinophil chemotaxis, while MIF antagonist and CXCR4 antagonist, AMD3100, revert this effect. In a model of EoE induced by ovalbumin, Mif-deficient mice have reduced inflammation and collagen deposition compared with wild-type (WT) mice. Importantly, treatment of WT mice with anti-MIF or with AMD3100 during the challenge phase prevents accumulation of eosinophils and tissue remodeling. Conversely, recombinant MIF promoted tissue eosinophil inflammation in allergic mice. Together, these results implicate MIF in the pathogenesis of esophageal inflammation and suggest that targeting MIF might represent a novel therapy for EoE.

Macrophage migration inhibitory factor: association of -794 CATT5-8 and -173 G>C polymorphisms with TNF-α in systemic lupus erythematosus.

Macrophage migration inhibitory factor (MIF) is an upstream immunoregulatory cytokine associated with the pathogenesis of autoimmune inflammatory diseases. There is evidence that MIF functions in a positive feedback loop with TNF-α that could perpetuate the inflammatory process in systemic lupus erythematosus (SLE). In this case-control study we investigated whether commonly occurring functional MIF polymorphisms are associated with SLE as well as with MIF and TNF-α serum levels in a Mexican-Mestizo population. Genotyping of the -794 CATT5-8 (rs5844572) and -173 G>C (rs755622) MIF polymorphisms was performed by PCR and PCR-RFLP, respectively in 186 SLE patients and 200 healthy subjects. MIF and TNF-α serum levels were determined by ELISA. A significant increase of MIF and TNF-α levels was found in SLE patients. According to a genetic model, we found a significant association of genotypes carrying the -794 CATT7 and -173(∗)C risk alleles with susceptibility to SLE and with a significant increase of TNF-α. In conclusion, MIF gene polymorphisms are associated with SLE susceptibility and with an increase of TNF-α serum levels in a Mexican-Mestizo population.

CD84 is a survival receptor for CLL cells.

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of CD5+ B lymphocytes in peripheral blood, lymphoid organs and bone marrow. The main feature of the disease is accumulation of the malignant cells due to decreased apoptosis. CD84 belongs to the signaling lymphocyte activating molecule family of immunoreceptors, and has an unknown function in CLL cells. Here, we show that the expression of CD84 is significantly elevated from the early stages of the disease, and is regulated by macrophage migration inhibitory factor and its receptor, CD74. Activation of cell surface CD84 initiates a signaling cascade that enhances CLL cell survival. Both downmodulation of CD84 expression and its immune-mediated blockade induce cell death in vitro and in vivo. In addition, analysis of samples derived from an on-going clinical trial, in which human subjects were treated with humanized anti-CD74 (milatuzumab), shows a decrease in CD84 messenger RNA and protein levels in milatuzumab-treated cells. This downregulation was correlated with reduction of Bcl-2 and Mcl-1 expression. Thus, our data show that overexpression of CD84 in CLL is an important survival mechanism that appears to be an early event in the pathogenesis of the disease. These findings suggest novel therapeutic strategies based on the blockade of this CD84-dependent survival pathway.

Platelets are a previously unrecognised source of MIF.

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine with chemokine-like functions and a role in atherogenesis. MIF is secreted by various cells including endothelial cells and macrophages. Platelets are another prominent cell type with a role in atherogenesis and are a rich source of atherogenic chemokines. We asked whether platelets express and secrete MIF. In comparison, CXCL12 release was determined. We examined the subcellular localisation of MIF in platelets/megakaryocytes, studied its co-localisation with other platelet-derived mediators and asked whether platelets contain MIF mRNA. Moreover, we probed the functional role of platelet-derived MIF in inflammatory cell recruitment. Using Western blot and ELISA, we demonstrated and quantitated MIF protein in human and mouse platelets. Applying confocal-microscopy, MIF was found to localise in granular-like structures, but did not co-localise with known platelet cytokines. qPCR indicated that platelets contain low levels of MIF mRNA. ELISA measurements from human platelet supernatants showed that, whereas thrombin and collagen triggered the release of MIF and CXCL12, ADP and oxidised LDL promoted CXCL12 but not MIF secretion. Using Transwell assays, we demonstrated that platelet supernatants promoted monocyte chemotaxis and that this was blocked by neutralising MIF antibodies.This is the first report demonstrating MIF secretion from activated platelets, suggesting that platelets are a previously unrecognised source of MIF in inflammatory processes. There are distinct activating stimuli for MIF and CXCL12 secretion. A substantial portion of the chemotactic capacity of stimulated platelet supernatants is contributed by MIF, suggesting a role for platelet-derived MIF in atherogenic cell recruitment.

Macrophage migration inhibitory factor (MIF): genetic evidence for participation in early onset and early stage rheumatoid arthritis.

Macrophage migration inhibitory factor (MIF) is an upstream pro-inflammatory cytokine that is associated with the pathogenesis of autoimmune inflammatory diseases including rheumatoid arthritis (RA). Two polymorphisms in the upstream region exist in the MIF gene and are associated with RA susceptibility or severity in different populations. In this case-control study, we investigated whether MIF polymorphisms are associated with RA susceptibility or activity in a western Mexican population .The relationship of MIF levels with clinical features of disease also was assessed. Genotyping of the -794 CATT5-8 (rs5844572) and the -173 G>C (rs755622) polymorphisms was performed by PCR and PCR-RFLP respectively on 226 RA patients and 210 healthy subjects. Serum MIF levels were determined by ELISA. We found a significant association between the -794 CATT5-8 6,7 MIF genotype with RA. Moreover, we detected an association between the -794 CATT7 allele with early onset RA. The -794 CATT7 and -173(*)C alleles, which are in linkage disequilibrium, were associated with high disease activity on RA patients. A positive correlation between circulating MIF levels and C-reactive protein, erythrocyte sedimentation rate, rheumatoid factor, anti-citrullinated protein/peptides antibodies and TNFα was detected. MIF levels appear to be associated with disease progression rather than disease activity, which is distinct from the established relationship between disease activity and TNFα levels. In conclusion, the MIF gene and protein are associated with RA in a western Mexican population, with a main contribution onto early onset and early stages of disease.

Distribution maps of D-dopachrome tautomerase in the mouse brain.

D-Dopachrome tautomerase is an enzyme related by amino acid sequence and catalytic activity to macrophage migration inhibitory factor. Both of these small molecules are pro-inflammatory cytokines mediating broad innate immune responses. Although it is well established that the gene product of D-dopachrome tautomerase is widely expressed in liver and kidney cells, no study has mapped the distribution pattern of this tautomeric enzyme in the mammalian nervous system. Here, we address this void by characterizing the cellular localization of D-dopachrome tautomerase in the adult mouse brain. Two well-characterized polyclonal antibodies were used for Western blotting and immunohistochemical localization of the endogenous tautomeric enzyme. Our results show that D-dopachrome tautomerase is present throughout the brain parenchyma with a large fraction of heterogeneous interneurons harboring a stable and robust expression of the enzyme. These data point to a potential involvement of D-dopachrome tautomerase activity in the mature mouse brain, and suggest some functional and evolutionary relationship between innate immunity and tautomerization of D-dopachrome in mammalian species.

Elevated levels of macrophage migration inhibitory factor in women with metabolic syndrome.

Metabolic syndrome is a complex clinical disorder characterized by obesity, a disturbance of glucose metabolism, dyslipidemia, and hypertension, leading to increased cardiovascular risk. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced both by innate immune cells and by adipocytes, and it plays an important role in inflammatory and cardiovascular diseases. The goal of this study was to evaluate the expression of circulating MIF in patients with metabolic syndrome. A study was conducted involving 172 persons who attended the Jeju National University Hospital Health Promotion Center. Among the 172 subjects, 88 patients with metabolic syndrome and 84 healthy control subjects were included. Serum MIF levels were considerably higher in patients with metabolic syndrome than in healthy subjects (mean±SEM, 1413.0-pg/ml±102.6 vs. 1077.0-pg/ml±-91.3, p=0.016). Among the metabolic syndrome patients, MIF levels were significantly increased in women (1403.0-pg/ml±114.2 vs. 921.3 pg/ml±117.3, p=0.005), but not in men. Even after further linear regression adjustment for age and body mass index, the expression of MIF for women with metabolic syndrome was still clearly elevated when compared to healthy subjects (p=0.011). Circulating MIF concentrations showed a gender disparity between healthy and metabolic syndrome subjects. An elevation of systemic MIF in women with metabolic syndrome may contribute to pathogenesis of metabolic syndrome or to the development of metabolic syndrome-related diseases, such as atherosclerosis and type 2 diabetes mellitus.

Macrophage migration inhibitory factor (MIF) gene polymorphisms are associated with increased prostate cancer incidence.

Recurrent or persistent inflammation has emerged as an important factor in cancer development. Overexpression of macrophage migration inhibitory factor (MIF), an upstream regulator of innate immunity with pleiotropic effects on cell proliferation, has been implicated in prostate cancer (CaP). Two polymorphisms in the promoter of the MIF gene (-173G to C transition and seven copies of the -794 CATT repeat) are associated with increased MIF expression in vivo and poor prognosis in autoimmune diseases. We conducted a retrospective analysis of 131 CaP patients and 128 controls from a group of Veterans' Administration patients undergoing routine prostate-specific antigen screening. Patients with CaP were enrolled regardless of treatment. Inclusion criteria for the control group were absence of documented diagnosis of cancer and/or chronic inflammation within patient computerized records. Logistic regression demonstrated a significant association between CaP and the -173G/C, the -173C/C and the -794 7-CATT MIF polymorphisms (P<0.001). Patients with the -794 7-CATT allele had an increased risk of CaP recurrence at 5 years. Individuals with -173G/C, -173C/C and -794 7-CATT MIF genotypes have an increased incidence of CaP and these genotypes may serve as an independent marker for cancer recurrence.

Macrophage migration inhibitory factor (MIF) promotes cell survival by activation of the Akt pathway and role for CSN5/JAB1 in the control of autocrine MIF activity.

The phosphoinositide-3-kinase (PI3K)/Akt signaling pathway plays an important role in cell survival and the development of cancer. Macrophage migration inhibitory factor (MIF) is a critical inflammatory cytokine that was recently associated with tumorigenesis and that potently inhibits apoptosis. This may involve inhibition of p53-dependent genes, but the initiating molecular mechanism of how MIF controls survival/apoptosis is unknown. Here, we show that MIF prevents apoptosis and promotes tumor cell survival by directly activating the Akt pathway. MIF enhanced Akt activity in primary and immortalized fibroblasts (MEF and NIH/3T3), HeLa cervix carcinoma cells and various breast cancer cell lines. Activation was abolished by kinase inhibitors Ly294002 and PP2 and in Src/Yes/Fyn(SYF)(-/-) and CD74(-/-)(MEFs), while being enhanced in CD74-overexpressing MEFs, demonstrating that the MIF-induced Akt pathway encompasses signaling through the MIF receptor CD74 and the upstream kinases Src and PI3K. Akt was activated by exogenous rMIF and autocrine MIF action, as revealed by experiments in MIF(-/-)MEFs and antibody blockade. siRNA knockdown of CSN5/JAB1, a tumor marker and MIF-binding protein, showed that JAB1 controls autocrine MIF-mediated Akt signaling by inhibition of MIF secretion. Akt activation by MIF led to phosphorylation of the proapoptotic proteins BAD and Foxo3a. Apoptosis inhibition by MIF was functionally associated with Akt activation as it was abolished by overexpression of the Akt pathway inhibitor PTEN and occurred independently of p53. This was shown by studying DNA damage-induced apoptosis in fibroblasts, the Fas death pathway in HeLa cells that do not express functional p53, and etoposide-induced apoptosis in breast carcinoma cells expressing mutant p53. Importantly, dependence of breast cancer cell survival on MIF correlated with Akt activation and the PTEN status of these cells. Thus, MIF can directly promote cell survival through activation of the PI3K/Akt pathway and this effect is critical for tumor cell survival.

Association between serum levels of soluble receptor for advanced glycation end products and circulating advanced glycation end products in type 2 diabetes.

AIMS/HYPOTHESIS: Activation of the receptor for advanced glycation end products (RAGE, also known as AGE-specific receptor [AGER]) has been implicated in the development of diabetic vascular complications. Blockade of RAGE using a soluble form of the receptor (sRAGE) suppressed vascular hyperpermeability and atherosclerosis in animal models. Since little is known about the regulation of endogenous sRAGE levels, we determined whether serum sRAGE is influenced by circulating AGEs and the severity of nephropathy in type 2 diabetic patients. MATERIALS AND METHODS: We recruited 150 healthy control and 318 diabetic subjects. Diabetic subjects were subdivided into those with proteinuria, microalbuminuria or normoalbuminuria. Serum sRAGE was assayed by ELISA and serum AGEs by competitive ELISA using a polyclonal rabbit antiserum raised against AGE-RNase. RESULTS: Diabetic subjects had higher sRAGE (1,029.5 pg/ml [766.1-1,423.0] interquartile range vs 1,002.6 [726.5-1,345.3], p<0.05) and AGEs (4.07+/-1.13, SD, unit/ml vs 3.39+/-1.05, p<0.01) than controls. Proteinuric subjects had the highest sRAGE levels and there was a significant trend between the severity of nephropathy and sRAGE (p=0.01). In diabetic subjects, serum log(sRAGE) correlated with AGEs (r=0.27, p<0.001), log(plasma creatinine) (r=0.31, p<0.001), log(urine AER) (r=0.24, p<0.01) and log(triglycerides) (r=0.15, p<0.01). On stepwise linear regression analysis, AGEs and creatinine levels were the main independent determinants of sRAGE concentration. CONCLUSIONS/INTERPRETATION: Serum sRAGE levels and circulating AGEs are associated with the severity of nephropathy in type 2 diabetic patients. Prospective studies are required to determine whether endogenous sRAGE potentially influences the development of diabetic vascular complications.

Ras transformation requires metabolic control by 6-phosphofructo-2-kinase.

Neoplastic cells transport large amounts of glucose in order to produce anabolic precursors and energy within the inhospitable environment of a tumor. The ras signaling pathway is activated in several cancers and has been found to stimulate glycolytic flux to lactate. Glycolysis is regulated by ras via the activity of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases (PFK2/FBPase), which modulate the intracellular concentration of the allosteric glycolytic activator, fructose-2,6-bisphosphate (F2,6BP). We report herein that sequential immortalization and ras-transformation of mouse fibroblasts or human bronchial epithelial cells paradoxically decreases the intracellular concentration of F2,6BP. This marked reduction in the intracellular concentration of F2,6BP sensitizes transformed cells to the antimetabolic effects of PFK2/FBPase inhibition. Moreover, despite co-expression of all four mRNA species (PFKFB1-4), heterozygotic genomic deletion of the inducible PFKFB3 gene in ras-transformed mouse lung fibroblasts suppresses F2,6BP production, glycolytic flux to lactate, and growth as soft agar colonies or tumors in athymic mice. These data indicate that the PFKFB3 protein product may serve as an essential downstream metabolic mediator of oncogenic ras, and we propose that pharmacologic inhibition of this enzyme should selectively suppress the high rate of glycolysis and growth by cancer cells.

Role for macrophage migration inhibitory factor in asthma.

Macrophage migration inhibitory factor (MIF) is an immunologic regulator that is expressed in inflammatory and autoimmune disorders. We investigated MIF's role in asthma using genetic approaches in a mouse model and in a cohort of asthma patients. Mice genetically deficient in MIF that were primed and aerosol-challenged with ovalbumin showed less pulmonary inflammation and lower airway hyperresponsiveness than genetically matched, wild-type controls. MIF deficiency also resulted in lower titers of specific IgE, IgG(1), and IgG(2a), and decreased pulmonary, T(H)2 cytokine levels. IL-5 concentrations were lower and corresponded to decreased eosinophil numbers in bronchoalveolar lavage fluid. T cell studies also showed a lower level of antigen-specific responses in MIF-KO versus wild-type mice. In an analysis of 151 white patients with mild, moderate, or severe asthma (Global Initiative for Asthma criteria), a significant association was found between mild asthma and the low-expression, 5-CATT MIF allele. Pharmacologic inhibition of MIF may be beneficial and could be guided by the MIF genotype of affected individuals.

The p53-dependent effects of macrophage migration inhibitory factor revealed by gene targeting.

Macrophage migration inhibitory factor (MIF) is a mediator of host immunity and functions as a high, upstream activator of cells within the innate and the adaptive immunological systems. Recent studies have suggested a potentially broader role for MIF in growth regulation because of its ability to antagonize p53-mediated gene activation and apoptosis. To better understand MIF's activity in growth control, we generated and characterized a strain of MIF-knockout (MIF-KO) mice in the inbred, C57BL/6 background. Embryonic fibroblasts from MIF-KO mice exhibit p53-dependent growth alterations, increased p53 transcriptional activity, and resistance to ras-mediated transformation. Concurrent deletion of the p53 gene in vivo reversed the observed phenotype of cells deficient in MIF. In vivo studies showed that fibrosarcomas induced by the carcinogen benzo[alpha]pyrene are smaller in size and have a lower mitotic index in MIF-KO mice relative to their WT counterparts. The data provide direct genetic evidence for a functional link between MIF and the p53 tumor suppressor and indicate an important and previously unappreciated role for MIF in carcinogenesis.

Macrophage migration inhibitory factor expression is increased in pituitary adenoma cell nuclei.

Macrophage migration inhibitory factor (MIF) is an essential regulator of the macrophage responses to endotoxin. MIF also has the ability to override the anti-inflammatory actions of glucocorticoids during an immune response, and is thus an important pro-inflammatory factor. The presence of MIF in cells of the anterior pituitary has been described, and high levels of MIF in other rapidly proliferating tIssues have also been demonstrated. It has been hypothesised that MIF release from these cells is influenced by the hypothalamo-pituitary-adrenal axis, and that ACTH and MIF are released simultaneously to exert counter-regulatory effects on cortisol. However, another intracellular role for MIF has also been suggested as it has been shown that MIF exerts an effect on the inhibitory cell cycle control protein p27 through an interaction with Jab1, a protein implicated in p27 degradation. We studied MIF expression in different normal and adenomatous human pituitary samples using immunohistochemistry and RT-PCR. There was evidence of co-immunoprecipitation of MIF with Jab1, suggesting an interaction of the two proteins. Our results showed that there is increased expression of MIF protein in the nuclei of all pituitary adenomas compared with normal tIssue (P=0.0067), but there was no statistically significant difference in nuclear MIF expression between the different adenoma types. Nuclear MIF expression correlated positively with p27 and its phosphorylated form in normal tIssue (P=0.0028 and P<0.0001); however, this relationship was not seen in the adenoma samples. Cytoplasmic expression of MIF was found to be variable both in normal and adenomatous samples, with no consistent pattern. MIF mRNA was demonstrated to be present in all tumour and normal samples studied. Somatotroph tumours showed higher MIF mRNA expression compared with normal pituitary or other types of adenomas. In conclusion, MIF is expressed in cell nuclei in pituitary adenomas to a greater extent than in normal pituitary tIssue. We speculate that it may play a role in the control of the cell cycle, but whether its higher level in adenomas is a cause or a consequence of the tumorigenic process remains to be clarified.

Macrophage migratory inhibitory factor (MIF) expression in acute graft-versus-host disease (GVHD) in allogeneic hemopoietic stem cell transplant recipients.

Graft-versus-host disease (GVHD) is a major complication after hemopoietic stem cell transplantation (HSCT), but its pathogenesis remains uncertain. Macrophage migratory inhibitory factor (MIF) is an important mediator in the allo-immune reaction during renal transplantation, yet its role in hemopoietic stem cell transplantation (HSCT) remains unexplored. This study investigated the potential role of MIF in acute graft-versus-host disease (aGVHD) following allogeneic HSCT. Forty-six randomly selected patients undergoing autologous or allogeneic HSCT were studied. Immunohistochemistry and in situ hybridization were performed to examine tissue MIF mRNA and protein expression on skin and colonic biopsy specimens. The associated T cell and macrophage activation was also studied by immunohistochemical studies. A semi-quantitative method was used to assess MIF staining, as well as T cell and macrophage staining. Serial blood samples were analyzed by ELISA for serum MIF levels. Immunohistochemistry and in situ hybridization performed in 15 skin and 19 colonic biopsies from 17 patients who developed moderate to severe aGVHD showed a significant increase in MIF mRNA and protein expression compared with normal controls (seven skin and five colonic biopsies). MIF was localized within the epidermis and the vascular area of skin, but diffusely expressed in the entire thickness of colon. Macrophage and T lymphocyte infiltration was confined to areas of strong MIF expression. Serial analysis by ELISA showed that only patients who developed aGVHD (n = 19) exhibited an increase (two- to three-fold) in serum MIF during HSCT, but not in the allogeneic HSCT recipients without aGVHD (n = 7) or those who received autologous HSCT (n = 8). In 14 out of 19 patients, serum MIF peaked before the onset of aGVHD. Local and systemic up-regulation of MIF expression is associated with the occurrence of acute GVHD. Its pathogenetic role remains to be further determined.