In vivo blockade of macrophage migration inhibitory factor prevents skin graft destruction after indirect allorecognition

Down-regulating cyclin-dependent kinase 9 of alloreactive CD4+ T cells prolongs allograft survival

CDK9 (Cyclin-dependent kinase 9)/Cyclin T1/RNA polymerase II pathway has been demonstrated to promote the development of several inflammatory diseases, such as arthritis or atherosclerosis, however, its roles in allotransplantation rejection have not been addressed. Here, we found that CDK9/Cyclin T1 were apparently up-regulated in the allogeneic group, which was positively correlated with allograft damage. CDK9 was inhibited obviously in naive splenic CD4⁺ T cells treated 6 h with 3 μM PHA767491 (a CDK9 inhibitor), and adoptive transfer of these CD4⁺ T cells into allografted SCID mice resulted in prolonged survival compared with the group without PHA767491 pretreated. Decelerated rejection was correlated with enhanced IL-4 and IL-10 production and with decreased IFN-γ production by alloreactive T cells. More interestingly, we found that CDK9₄₂, not CDK9₅₅, was high expressed in allorejection group, which could be prominently dampened with PHA767491 treatment. The expression of CDK9₄₂ was consistent with its downstream molecule RNA polymerase II. Altogether, our findings revealed the crucial role of CDK9/Cyclin T1/Pol II pathway in promoting allorejection at multiple levels and may provide a new approach for transplantation tolerance induction through targeting CDK9.

Age-dependent alterations in the inflammatory response to pulmonary challenge

The aging lung is increasingly susceptible to infectious disease. Changes in pulmonary physiology and function are common in older populations, and in those older than 60 years, pneumonia is the major cause of infectious death. Understanding age-related changes in the innate and adaptive immune systems, and how they affect both pulmonary and systemic responses to pulmonary challenge are critical to the development of novel therapeutic strategies for the treatment of the elderly patient. In this observational study, we examined age-associated differences in inflammatory responses to pulmonary challenge with cell wall components from Gram-positive bacteria. Thus, male Sprague–Dawley rats, aged 6 months or greater than 18 months (approximating humans of 20 and 55–65 years), were challenged, intratracheally, with lipoteichoic acid and peptidoglycan. Cellular and cytokine evaluations were performed on both bronchoalveolar lavage fluid (BAL) and plasma, 24 h post-challenge. The plasma concentration of free thyroxine, a marker of severity in non-thyroidal illness, was also evaluated. The older animals had an increased chemotactic gradient in favor of the airspaces, which was associated with a greater accumulation of neutrophils and protein. Furthermore, macrophage migration inhibitory factor (MIF), an inflammatory mediator and putative biomarker in acute lung injury, was increased in both the plasma and BAL of the older, but not young animals. Conversely, plasma free thyroxine, a natural inhibitor of MIF, was decreased in the older animals. These findings identify age-associated inflammatory/metabolic changes following pulmonary challenge that it may be possible to manipulate to improve outcome in the older, critically ill patient.

Anti‑migratory effect of rapamycin impairs allograft imaging by 18F‑fluorodeoxyglucose‑labeled splenocytes

Tracking lymphocyte migration is an emerging strategy for non‑invasive nuclear imaging of allografts; however, its clinical application remains to be fully demonstrated. In the present study, the feasibility of using rapamycin‑treated 18F‑fluorodeoxyglucose (18F‑FDG)‑labeled splenocytes for the in vivo imaging of allografts was evaluated. C57BL/6 skin was heterotopically transplanted onto non‑obese diabetic/severe combined immunodeficient recipient mice. BALB/c 18F‑FDG‑labeled splenocytes with or without rapamycin pretreatment (designated as FR and FC cells, respectively) were transferred into recipient mice 30 days later. Imaging of radiolabeled cells in the skin grafts was conducted through in vivo dynamic whole‑body phosphor‑autoradiography and histological analysis. Notably, rapamycin impaired the migration of 18F‑FDG‑labeled splenocytes to the graft. At all time points, the radioactivity of allografts (digital light units/mm2) was significantly lower in the group that received FR cells, compared with the group that received FC cells (P<0.01). Furthermore, the peak allograft to native skin ratio was 1.29±0.02 at 60 min for the FR group and 3.29±0.17 at 30 min for the FC group (P<0.001). In addition, the in vivo radioactivity of the allografts was observed to be correlated with the transferred cells, which were observed histologically (r2=0.887; P<0.0001). Although 18F‑FDG‑labeled splenocytes migrated to the allograft, imaging of these cells may not be possible in the presence of rapamycin.

In vivo Toll-like receptor 5 (TLR5) imaging with radiolabeled anti-TLR5 monoclonal antibody in rapamycin-treated mouse allogeneic skin transplantation model

BACKGROUND

In organ transplantation, increasing evidence, both in experimental and human studies, indicates that Toll-like receptor (TLR) activation is involved in the innate immune recognition of allograft. TLR5, the only protein recognition receptor of TLRs, is indicated potentially to be the immune regulation target. This study was designed to determine whether TLR5 could be a biomarker for in vivo allograft visualization, after immunosuppressant rapamycin treatment, using radiolabeled sodium iodide ((131) I)-anti-TLR5 monoclonal antibody (mAb).

METHODS

BALB/c mice were transplanted with C57BL/6 skin, with/without rapamycin treatment (the rapamycin-treated group and the phosphate buffered saline [PBS]-rejection group, respectively). In vivo dynamic whole-body phosphor-autoradiography and ex vivo biodistribution studies were conducted after (131) I-anti-TLR5 mAb injection.

RESULTS

Dynamic phosphor-autoradiography imaging showed clear graft localization from 12 h onward. At 72 h after injection, graft uptake quantified from images was higher for the rapamycin-treated group (26,448 ± 904 digital light units [DLU]/mm(2) ), compared with the PBS-treated allo-rejection group (9176 ± 576 DLU/mm(2) ). Treatment with anti-TLR5 mAb inhibited graft uptake. Organ biodistribution study reflected the same tendency, and (131) I-anti-TLR5 mAb uptake reached a maximum of 12.05 ± 1.86 %ID/g (percent injected dose per gram) at 1 h, and graft-to-native skin ratio reached 8.10 ± 0.10 %ID/g at 72 h after injection in rapamycin-treated grafts.

CONCLUSION

Radiolabeled anti-TLR5 mAb showed higher uptake in allo-treated grafts compared with allo-rejection grafts, which was proved by non-invasive dynamic phosphor-autoradiography imaging, and invasive ex vivo biodistribution. Radiolabeled anti-TLR5 mAb is a new tracer for non-invasive in vivo imaging of TLR5 in rapamycin-treated allograft.

Innate immunity and resistance to tolerogenesis in allotransplantation

The development of immunosuppressive drugs to control adaptive immune responses has led to the success of transplantation as a therapy for end-stage organ failure. However, these agents are largely ineffective in suppressing components of the innate immune system. This distinction has gained in clinical significance as mounting evidence now indicates that innate immune responses play important roles in the acute and chronic rejection of whole organ allografts. For instance, whereas clinical interest in natural killer (NK) cells was once largely confined to the field of bone marrow transplantation, recent findings suggest that these cells can also participate in the acute rejection of cardiac allografts and prevent tolerance induction. Stimulation of Toll-like receptors (TLRs), another important component of innate immunity, by endogenous ligands released in response to ischemia/reperfusion is now known to cause an inflammatory milieu favorable to graft rejection and abrogation of tolerance. Emerging data suggest that activation of complement is linked to acute rejection and interferes with tolerance. In summary, the conventional wisdom that the innate immune system is of little importance in whole organ transplantation is no longer tenable. The addition of strategies that target TLRs, NK cells, complement, and other components of the innate immune system will be necessary to eventually achieve long-term tolerance to human allograft recipients.

Macrophage migration inhibitory factor (MIF): a key player in protozoan infections

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine produced by the pituitary gland and multiple cell types, including macrophages (Mø), dendritic cells (DC) and T-cells. Upon releases MIF modulates the expression of several inflammatory molecules, such as TNF-α, nitric oxide and cyclooxygenase 2 (COX-2). These important MIF characteristics have prompted investigators to study its role in parasite infections. Several reports have demonstrated that MIF plays either a protective or deleterious role in the immune response to different pathogens. Here, we review the role of MIF in the host defense response to some important protozoan infections.

MIF: a key player in cutaneous biology and wound healing

Owing to its implication in a range of pathological conditions, including asthma, rheumatoid arthritis, atherosclerosis, inflammatory bowel disease and cancer, the pleiotropic cytokine macrophage migration inhibitory factor (MIF) has been the subject of intensive recent investigation. In the field of dermatology, MIF is believed to be a detrimental factor in diseases such as systemic sclerosis, atopic dermatitis, psoriasis, eczema and UV radiation damage. However, its contribution to other aspects of cutaneous biology is currently unclear. Although its expression in intact skin is well characterized, little is known about MIF's role in cutaneous homoeostasis. However, recent data do identify MIF as a key player in the immune privilege of hair follicles. Similarly, although MIF is rapidly released and its local expression significantly induced upon wounding, its primary role in the ensuing repair process remains a source of contention. MIF has been identified as being a key effector of the beneficial effects of estrogen on wound repair, yet studies employing Mif null mice, recombinant MIF, and neutralizing anti-MIF antibodies have failed to provide a consensus as to whether it benefits or inhibits healing. In fact MIF appears to be able to exert both positive and negative effects, with the cell-specific relevancy of MIF in wound healing still unclear. Thus, if MIF and/or its downstream targets are to be therapeutically useful in the context of cutaneous repair, more needs to be done to establish the nature and mechanism of action of MIF and its receptors in healing wounds.

Alternatively Expressed Genes Identified in the CD4+ T Cells of Allograft Rejection Mice

Allograft rejection is a leading cause for the failure of allotransplantation. CD4+ T cells play critical roles in this process. The identification of genes that alternatively expressed in CD4+ T cells during allograft rejection will provide critical information for studying the mechanism of allograft rejection, finding specific gene markers for monitoring, predicting allograft rejection, and opening new ways to regulate and prevent allograft rejection. Here, we established allograft and isograft transplantation models by adoptively transferring wild-type BALB/c mouse CD4+ T cells into severe combined immunodeficient (SCID) mice with a C57BL/6 or BALB/c mouse skin graft. Using the whole transcriptome sequencing-based serial analysis of gene expression (SAGE) technology, we identified 97 increasingly and 88 decreasingly expressed genes that may play important roles in allograft rejection and tolerance. Functional classification of these genes shows that apoptosis, transcription regulation, cell growth and maintenance, and signal transduction are among the frequently changed functional groups. This study provides a genome-wide view for the candidate genes of CD4+ T cells related to allotransplantation, and this report is a good resource for further microarray studies and for identifying the specific markers that are associated with clinical organ transplantations.

The role of macrophage migration inhibitory factor in mouse islet transplantation

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced by many tissues including pancreatic beta-cells.

METHODS

This study investigates the impact of MIF on islet transplantation using MIF knock-out (MIFko) mice.

RESULTS

Early islet function, assessed with a syngeneic marginal islet mass transplant model, was enhanced when using MIFko islets (P<0.05 compared with wild-type [WT] controls). This result was supported by increased in vitro resistance of MIFko islets to apoptosis (terminal deoxynucleotide tranferase-mediated dUTP nick-end labeling assay), and by improved glucose metabolism (lower blood glucose levels, reduced glucose areas under curve and higher insulin release during intraperitoneal glucose challenges, and in vitro in the absence of MIF, P<0.01). The beneficial impact of MIFko islets was insufficient to delay allogeneic islet rejection. However, the rejection of WT islet allografts was marginally delayed in MIFko recipients by 6 days when compared with WT recipient (P<0.05). This effect is supported by the lower activity of MIF-deficient macrophages, assessed in vitro and in vivo by cotransplantation of islet/macrophages. Leukocyte infiltration of the graft and donor-specific lymphocyte activity (mixed lymphocyte reaction, interferon gamma ELISPOT) were similar in both groups.

CONCLUSION

These data indicate that targeting MIF has the potential to improve early function after syngeneic islet transplantation, but has only a marginal impact on allogeneic rejection.

The role of macrophage migration inhibitory factor on glucose metabolism and diabetes

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine involved in many inflammatory reactions and disorders, and it has become evident that it also affects glucose homeostasis. The protein is produced by pancreatic beta cells and can promote the release of insulin. It also modulates glucose uptake, glycolysis and insulin resistance in insulin target cells such as the adipocyte, myocyte and cardiomyocyte. Possessing both immunological and endocrinological properties, MIF has been associated with the development of type 1 and type 2 diabetes, and it may be important in the setting of islet transplantation. The present review summarises our current knowledge, based on clinical and research data, on the impact of MIF on both physiological and pathological aspects of glucose metabolism.

NK cells contribute to the skin graft rejection promoted by CD4+ T cells activated through the indirect allorecognition pathway

Rejection of solid organ allografts is promoted by T cells. Recipient T cells can directly recognize intact allo-MHC molecules on donor cells and can also indirectly recognize processed donor-derived allo-peptides presented by recipient antigen-presenting cells in the context of self-MHC molecules. Although CD4(+) T cells primed through the indirect allorecognition pathway alone are sufficient to promote acute allograft rejection, it is unknown how they can mediate graft destruction without cognate recognition of donor cells. In this study, we analyzed the indirect effector mechanism of skin allograft rejection using a mouse model in which SCID recipients bearing MHC class II-deficient skin allografts were adoptively transferred with CD4(+) T cells. Histologically, entire graft necrosis was preceded by mononuclear cell infiltration in the graft epithelia with epithelial cell apoptosis, indicating cell-mediated cytotoxicity against donor cells as an effector mechanism. Beside CD4(+) T cells and macrophages, NK cells infiltrated in the rejecting grafts. Depletion of NK cells as well as blocking of the activating NK receptor NKG2D allowed prolonged survival of the grafts. Expression of NKG2D ligands was up-regulated in the rejecting grafts. These results suggest that NK cells activated through NKG2D contribute to the skin allograft rejection promoted by indirectly primed CD4(+) T cells.

Blockage of the macrophage migration inhibitory factor expression by short interference RNA inhibited the rejection of an allogeneic tracheal graft

We investigated the inhibitory effect of blocking the macrophage migration inhibitory factor (MIF) on the fibrous obstruction of a transplanted allograft in a murine model of obstructive bronchiolitis (OB). Tracheal grafts from C57BL/6 mice were transplanted into a subcutaneous pouch of BALB/c. Three days after transplantation, liposome including short interference (si) RNA for MIF was injected into the lumen of the grafts. The allografts were then harvested 7, 14 or 28 days after transplantation for an evaluation of the morphological changes. The MIF expression, which was ubiquitously recognized in the epithelium of allografts, decreased after the in vivo transfection of MIF siRNA. OB formation was therefore inhibited significantly more by the treatment with MIF siRNA than the allografts injected with empty liposome on the 14th day, however, no difference was observed between them on the 28th day. Treatment with MIF siRNA inhibits the destruction of tracheal allografts and OB formation in the early phase, and MIF was thus found to be one of the major cytokines involved in the rejection of the allogeneic trachea.

Blockade of macrophage migration inhibitory factor (MIF) in Schistosoma japonicum-infected mice results in an increased adult worm burden and reduced fecundity

Macrophage migration inhibitory factor (MIF), a cytokine produced by many cell types, modulates cellular and humoral immune responses. In schistosomiasis, ova in the portal circulation induce a delayed type hypersensitivity (DTH) that results in formation of hepatic granulomas (HG) which secrete MIF activity. Therefore, we hypothesized that endogenous MIF modulates immune responses in schistosomiasis. To test this hypothesis, Schistosoma japonicum-infected mice were injected with rabbit IgG or neutralizing rabbit IgG antibody to MIF 4.5-6.5 week post infection when HG form and female worms are laying eggs. Compared with controls, 6.5-7-week post-infection, antibody-treated mice had 1.7-3 times as many adult worms and half as many ova per worm pair in their livers. In contrast, antibody introduced before infection or 6-8 week post infection did not affect worm burden or fecundity. Thus, for the first time there is evidence that 4.5-6 week post-infection endogenous MIF somehow mediates reduction of adult worm burden and promotes fecundity. Splenocytes and HG cells from antibody-treated mice showed reduced intracellular expression of TNFalpha and/or IL-10. We hypothesize that endogenous MIF enhances adult worm attrition by up-regulating innate and adaptive immune responses by increasing expression of MHC-II, co-stimulatory, adhesion, receptor and cytokine molecules, and promotes fecundity by up-regulating TNFalpha expression.

Blockade of macrophage migration inhibitory factor does not prevent acute renal allograft rejection

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory molecule involved in cell-mediated immunity and delayed-type hypersensitivity (DTH). We inhibited systemic and local MIF production to determine its contribution to acute rejection (AR). Skin DTH response and acute rejection of skin and kidney allografts were examined using MIF gene knockout (MIF -/-) and wild-type mice (MIF +/+) with anti-MIF or control antibody. MIF-Ab reduced skin DTH by 60% (p < 0.01), but absence of the MIF gene (MIF -/-) had no effect. Local absence of MIF had no effect on the survival of skin grafted onto BALB/c recipients. Similarly MIF +/+ and MIF -/- kidneys transplanted into BALB/c recipients showed a similar degree of histological rejection, graft dysfunction and cellular infiltrate suggesting that AR is not dependent on local MIF production. To investigate the influence of systemic MIF, BALB/c donor skin was grafted onto MIF +/+ and MIF -/- mice. The tempo of AR was not altered by systemic absence of MIF (MIF-Ab or MIF -/-). BALB/c kidneys transplanted into MIF +/+ (with or without MIF-Ab) and MIF -/- mice showed similar parameters of rejection. MIF blockade reduces the DTH response; however, neither local nor systemic MIF are required for the rejection of fully mismatched skin and renal allografts.

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.

Cardiac allograft rejection in the absence of macrophage migration inhibitory factor

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a secreted proinflammatory lymphokine essential for elicitation of delayed-type hypersensitivity (DTH) reactions in vivo. We tested whether MIF blockade-absence affected acute or chronic murine cardiac allograft rejection.

METHODS

Wild-type (WT) C57BL/6 (B6) mice underwent transplantation with BALB/c hearts with or without blocking anti-MIF antibody, and MIF knockout (KO) B6 mice underwent transplantation with MIF KO BALB/c hearts. Chronic immune injury was induced in WT and KO recipients using donor-specific transfusion and anti-CD40L antibody.

RESULTS

Unexpectedly, the blockade or genetic absence of MIF did not prolong graft survival even if recipient T-cell cytotoxicity was additionally impaired. The histologic manifestations of acute and chronic immune injury to the allograft were similar between groups.

CONCLUSIONS

MIF is not required for acute or chronic allograft rejection in mice. The findings raise questions about the role of DTH as an important mediator of cardiac allograft injury.

Carbon monoxide induces cytoprotection in rat orthotopic lung transplantation via anti-inflammatory and anti-apoptotic effects

Successful lung transplantation has been limited by the high incidence of acute graft rejection. There is mounting evidence that the stress response gene heme oxygenase-1 (HO-1) and/or its catalytic by-product carbon monoxide (CO) confers cytoprotection against tissue and cellular injury. This led us to hypothesize that CO may protect against lung transplant rejection via its anti-inflammatory and antiapoptotic effects. Orthotopic left lung transplantation was performed in Lewis rat recipients from Brown-Norway rat donors. HO-1 mRNA and protein expression were markedly induced in transplanted rat lungs compared to sham-operated control lungs. Transplanted lungs developed severe intraalveolar hemorrhage, marked infiltration of inflammatory cells, and intravascular coagulation. However, in the presence of CO exposure (500 ppm), the gross anatomy and histology of transplanted lungs showed marked preservation. Furthermore, transplanted lungs displayed increased apoptotic cell death compared with the transplanted lungs of CO-exposed recipients, as assessed by TUNEL and caspase-3 immunostaining. CO exposure inhibited the induction of IL-6 mRNA and protein expression in lung and serum, respectively. Gene array analysis revealed that CO also down-regulated other proinflammatory genes, including MIP-1alpha and MIF, and growth factors such as platelet-derived growth factor, which were up-regulated by transplantation. These data suggest that the anti-inflammatory and antiapoptotic properties of CO confer potent cytoprotection in a rat model of lung transplantation.

Xenogeneic skin graft rejection in M-CSF/macrophage deficient osteopetrotic mice

BACKGROUND

The cellular infiltrate in xenografts suggests that macrophages may be involved in xenograft rejection. However, the precise role of macrophages in xenograft rejection has not yet been fully addressed.

METHODS

Xenogeneic rat skin grafts were transplanted to macrophage colony stimulating factor (M-CSF)/macrophage-deficient osteopetrotic ([OP]-/-) and wild-type control mice. Skin graft survival and antidonor rat humoral responses were quantified.

RESULTS

Xenogeneic rat skin grafts survived 13 days in wild-type control mice, survival of rat skin grafts was significantly prolonged to 24 days in [OP]-/- mice (P<0.01). Similar results were observed in sensitized [OP]-/- and control mouse recipients, showing markedly prolonged rat skin graft survival in [OP]-/- mice. Levels of T-cell-dependent antirat antibodies [immunoglobulin G (IgG)2a and IgG3] in sera of [OP]-/- mice were significantly lower than that of control mice 2 weeks post-rat skin grafting. The proliferative responses to xenogeneic rats not to allogeneic mouse stimulation of T cells from [OP]-/- mice were significantly lower than that of wild-type mice. However, neutrilization of M-CSF by anti-M-CSF monoclonal antibody (mAb) or the addition of M-CSF to the in vitro culture systems of wild-type or [OP]-/- mouse T-responder cells, respectively, did not significantly change proliferative responses and cytolytic function against xenogeneic rat targets of wild-type or [OP]-/- mouse T-responder cells.

CONCLUSIONS

The in vitro data indicate that M-CSF does not directly regulate cellular immune responses to xenoantigens. The present studies indicate that macrophages may play an important role in immune rejection of xenografts. The precise role of macrophages in xenograft rejection should be further investigated.

Macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a ubiquitous protein that is found in virtually all cells. Its precise function in the majority of cells is not known, but studies performed over the last decade indicate that it is a critical upstream regulator of the innate and acquired immune response. MIF is released under a variety of circumstances, regulates cytokine secretion and the expression of receptors that are involved in innate immunity, inhibits p53 function, and activates components of the mitogen-activated protein kinase and Jun-activation domain-binding protein-1 (Jab-1) pathways. Compelling in vitro and in vivo evidence has focused attention on this protein as a new therapeutic target for inflammatory and autoimmune diseases. Unique structural features, including an intrinsic catalytic activity, offer attractive opportunities for the discovery and design of therapeutic MIF inhibitors.

Blockade of macrophage colony-stimulating factor reduces macrophage proliferation and accumulation in renal allograft rejection

Macrophage accumulation within an acutely rejecting allograft occurs by recruitment and local proliferation. To determine the importance of M-CSF in driving macrophage proliferation during acute rejection, we blocked the M-CSF receptor, c-fms, in a mouse model of acute renal allograft rejection. C57BL/6 mouse kidneys (allografts, n = 20) or BALB/c kidneys (isografts, n = 5) were transplanted into BALB/c mice. Anti-c-fms antibody (AFS98) or control Ig (50 mg/kg/day, i.p.) was given daily to allografts from days 0-5. All mice were killed day 6 postoperatively. Expression of the M-CSF receptor, c-fms, was restricted to infiltrating CD68+ macrophages. Blockade of c-fms reduced proliferating (CD68+/BrdU+) macrophages by 82% (1.1 v 6.2%, p < 0.001), interstitial CD68+ macrophage accumulation by 53% (595 v 1270/mm2, p < 0.001), and glomerular CD68+ macrophage accumulation by 71% (0.73 V 2.48 CD68+ cells per glomerulus, p < 0.001). Parameters of T-cell involvement (intragraft CD4+, CD8+ and CD25+ lymphocyte numbers) were not affected. The severity of tubulointerstitial rejection was reduced in the treatment group as shown by decreased tubulitis and tubular cell proliferation. Macrophage proliferation during acute allograft rejection is dependent on the interaction of M-CSF with its receptor c-fms. This pathway plays a significant and specific role in the accumulation of macrophages within a rejecting renal allograft.

In vitro and in vivo regulation by macrophage migration inhibitory factor (MIF) of expression of MHC-II, costimulatory, adhesion, receptor, and cytokine molecules

The secretion of macrophage migration inhibitory factor (MIF) is enhanced by inflammatory and other stimuli. MIF regulates innate and adaptive immune responses, but the mechanisms of this regulation are poorly understood. Our hypothesis was that MIF generated by these stimuli regulates these responses by modulating key molecular expression. This hypothesis was tested by adding greater than constitutive concentrations of recombinant MIF to cultures of various cell types and flow cytometric assay. MIF modulated surface expression of MHC-II, B7-2, CD40, CD40 ligand, ICAM-1 and Fcgamma, CR1/CR2, and IL-10 receptors and intracellular expression of IL-10, TNFalpha, and p40 (IL-12). MIF increased expression of B7-1 by B cells and CD40 L by T cells in spleens from Schistosoma mansoni-infected mice. Footpad injection of MIF reduced expression of MHC-II and CD40 by B cells in draining lymph nodes. Footpad injection of Mab to MIF reduced expression of B7-2 and CR1/CR2 by B cells and B7-2 by macrophages in these nodes. These data support our hypothesis.