Modulation of LPS-induced pulmonary neutrophil infiltration and cytokine production by the selective PPARbeta/delta ligand GW0742.

OBJECTIVE: To define the anti-inflammatory effects of PPARbeta/delta activation by use of the selective PPARbeta/delta ligand (GW0742) in a model of lipopolysaccharide (LPS)-induced pulmonary inflammation. METHODS: Male BALB/c mice were pretreated for three days with the PPARbeta/delta agonist, GW0742, prior to induction of LPS-mediated pulmonary inflammation. Bronchial alveolar lavage fluid (BALF) was analyzed for inflammatory cell influx and for levels of pro-inflammatory mediators. BALF-derived inflammatory cells were also collected for mRNA analysis. RESULTS: Pretreatment with GW0742 resulted in a significant decrease in leukocyte recruitment into the pulmonary space. Protein and mRNA levels of the pro-inflammatory cytokines IL-6, IL-1beta and TNFalpha in BALF were found to be significantly decreased in GW0742-treated animals (30 mg/kg). A significant decrease in granulocyte macrophage-colony stimulating factor (GM-CSF), a major regulator of neutrophil chemotaxis (via its downstream actions on TNFalpha and other cytokines/chemokines), activation and survival, was also noted in the BALF levels of GW0742-treated animals. CONCLUSIONS: The present study demonstrates that activation of PPARbeta/delta attenuates the degree of inflammation in a model of LPS-induced pulmonary inflammation and may therefore represent a novel therapeutic approach for the treatment of inflammation-mediated pathologies.

CD4+ T cells are critical for corneal, but not skin, allograft rejection.

BACKGROUND: The relative contribution of CD4+ or CD8+ T cells in allograft rejection remains to be fully characterized. Some reports indicate that there is an absolute requirement for CD4+ T cells in allogeneic rejection, whereas others report that CD4-depleted mice are capable of rejecting certain types of allografts. METHODS: We compared the ability of CD4- knockout (KO), CD8- KO, and normal CD4+/CD8+ mice to reject allogeneic corneal or skin grafts. We also examined delayed-type hypersensitivity and CTL responses to donor alloantigens. RESULTS: Engraftment of C57BL/6 corneas to C.B6-(n5-7) CD4-KO mice resulted in significantly higher rates of acceptance (>85%) than either C.B6-(n5-7) CD8- KO (30%) or normal BALB/c mice (40%). Likewise, mean survival times for B6 skin grafts placed on C.B6-(n5-7) CD4- KO mice (29.2 +/- 3.5 days) were significantly increased over those of normal BALB/c mice (13.2 +/- 1 days), although most CD4- KO mice (70%) eventually reject their grafts. C.B6-(n5-7) CD4- KO mice that reject allogeneic grafts fail to develop a delayed-type hypersensitivity response, but they did demonstrate significantly greater cytotoxic T lymphocyte precursor (CTLp) frequencies than did CD4- KO mice that accepted such grafts or that were not grafted. CONCLUSIONS: This study indicates that mice lacking CD4+ T cells have a significantly impaired ability to reject corneal allografts, but are able, in most cases, to reject allogeneic skin grafts. Thus, in the absence of CD4+ T cells, the likely mechanism for rejection appears to involve the generation of CD8+ CTLs.

Enhanced IL-10 and decreased IL-2 production after orthotopic corneal transplantation in mice.

Corneas from mice incompatible at both major histocompatibility complex (MHC) and non-MHC antigens were grafted orthotopically to unmodified and high-risk recipients. Production of interleukin-2 (IL-2) and IL-10 by cells from spleens and draining lymph nodes from corneal graft recipients was determined in vitro. Over 90% of corneal allografts suffered alloantigen-induced inflammatory reaction within the second or third week after surgery. However, only 56 % of grafts in unmodified and 75 % of grafts in high-risk recipients were irreversibly rejected. Cells obtained from draining lymph nodes from the vicinity of the eye of the corneal graft recipients produced significantly elevated amounts of IL-10 and decreased amounts of IL-2. This shift to the Th2 type cytokine response was observed after stimulation of the cells with graft donor MHC antigens, but not after stimulation with donor non-MHC or third-party alloantigens. No changes in cytokine production were detected in spleen. The enhancement of IL-10 production in the vicinity of the eye was a consequence of corneal grafting and did not correlate with the fate of the graft. The results thus show that orthotopic corneal transplantation induces a local shift to the Th2 type cytokine response, which might be considered another factor that contributes to the unique characteristics of the immunity in the eye and to the tolerance of an unusually high percentage of corneal allografts.

The effect of urocanic acid on graft rejection in an experimental model of orthotopic corneal transplantation in rabbits.

BACKGROUND: Urocanic acid (UCA) is a natural component of the stratum corneum of the skin. It has been described as a photoreceptor for ultraviolet B radiation. UCA is present in the skin as a trans-isomer and undergoes UVB irradiation-dependent isomerization from trans-to cis-isomer. An immunosuppressive effect of irradiated UCA, i.e. a mixture of cis- and trans-isomers, has been demonstrated both in vivo and in vitro. The aim of this study was to evaluate an immunosuppressive effect of irradiated UCA on graft rejection in an experimental model of orthotopic corneal transplantation. METHOD: A commercially available UCA was dissolved in salt solution and irradiated by XeCl excimer laser beam in order to obtain a mixture of cis- and trans-isomers. The immunosuppressive effect of irradiated UCA, compared to controls, unirradiated UCA and salt solution, was evaluated in a high-risk orthotopic corneal transplantation model; the agents were administered subconjunctivally to rabbits. RESULTS: The rejection reaction was observed in all animals. The mean graft survival time in rabbits administered salt solution or unirradiated UCA was 20 days and 22 days, respectively. The irradiated solution of UCA significantly (P < 0.01, Mantel-Cox test) prolonged mean graft survival time to 29 days. CONCLUSION: Subconjunctival administration of irradiated UCA prolonged the graft survival time in comparison with unirradiated UCA or salt solution in recipients in a rabbit transplantation model. Although further studies are necessary, UCA seems to be an effective immunosuppressive drug after corneal transplantation.

[The significance of gender incompatibility in donors and recipients and the role of minor histocompatibility antigens in corneal transplantation]. / Význam inkompatibility pohlaví dárce a príjemce a role vedlejsích histokompatibilitních antigenu u transplantace rohovky.

AIM: The present study evaluates the ability of single male H-Y antigen to elicit corneal graft rejection or to prime recipient with subsequent induction of second-set corneal graft rejection in mice. Results were compared with the survival rates of orthotopic corneal grafts disparate at multiple minor histocompatibility (H) antigens and with syngeneic grafts. METHODS: A/Ph male or B10.A female and A/Ph female corneas were grafted onto A/Ph female mice. During the fourth week after grafting all acceptors of H-Y disparate grafts received the second corneal graft from the same donor. All grafts were evaluated three times a week during the period of nine weeks. RESULTS: Both first and second orthotopic corneal grafts incompatible at H-Y antigen did not display and sign of rejection reaction during the whole observation period and were accepted indefinitely. The rate of rejection reaction of grafts incompatible at multiple minor H antigens was 83%. Thirty-three percent of these grafts underwent rejection irreversibly. CONCLUSIONS: Single H-Y antigen disparity between corneal graft donor and recipient neither led to rejection of first grafts nor primed recipients as shown by tolerance of 100% of second-set grafts. Experiments demonstrated that incompatibility of sex between donor and recipient does not play role in corneal graft rejection. However, incompatibility at multiple minor H antigens led to the rejection reaction in 83% of first grafts and 33% of these grafts failed.

Transplantation immunity and tolerance in the eye: rejection and acceptance of orthotopic corneal allografts in mice.

The eye has been considered for a long time as a privileged site, where the normal immune response is not manifested. Using a model of orthotopic corneal allografts in mice we demonstrate that both transplantation immunity and tolerance are expressed in the eye. In two strain combinations, one having genetic disparities at the major histocompatibility complex (MHC) and non-MHC antigens and the other with antigenic differences only in non-MHC antigens, survival of corneal allografts was evaluated in normal unmodified recipients, in recipients presensitized with a skin allograft, and in mice made specifically tolerant to the donor alloantigens. While the corneal allografts in unmodified recipients underwent rejection leading to graft failure in 40-50% of the recipients, all corneal allografts in presensitized recipients were rejected. On the contrary, corneal allografts performed in neonatally tolerant recipients enjoyed survival comparable to that of syngeneic grafts. No significant differences in corneal allograft survival were found between MHC antigen compatible and MHC antigen incompatible strain combinations. The results demonstrate that transplantation immunity and tolerance are efficiently expressed in the eye. Consequently, the local regulatory mechanisms must be responsible for the characteristics of immunity after intraocular immunization and for a high degree of acceptance of corneal allografts in normal recipients.

Immunosuppressive effect of bovine seminal ribonuclease on a model of corneal transplantation in rabbit.

BACKGROUND: Bovine seminal ribonuclease (BS RNase) was determined to have a specific suppressive effect on the proliferation of T lymphocytes in vitro. Its immunosuppressive effect was proven in skin grafting in mice as well. METHODS: The immunosuppressive effect of BS RNase was evaluated in tissue cultures and on a model of corneal transplantation in rabbits. The penetration of BS RNase into the anterior chamber was detected by immunoblotting of anterior chamber fluid obtained from animals treated either topically or subconjunctivally. RESULTS: In vitro blastic transformation of mouse T lymphocytes was significantly inhibited by BS RNase (concentrations 15-250 micrograms/ml). No such effect was observed on B lymphocytes. In the rabbit model of corneal graft rejection, BS RNase injected subconjunctivally prolonged mean graft survival time significantly (33.4 days) compared with placebo (salt solution; MST 17.7 days). No BS RNase was detected by immunoblotting in anterior chamber fluid after either topical or subconjunctival application. CONCLUSION: BS RNase showed significant immunosuppressive effect both in the blastic transformation test and in the rabbit high-risk model of corneal transplantation. Negative results of anterior chamber fluid immunoblotting indicate poor absorption of the drug.

The role of major and minor histocompatibility antigens in orthotopic corneal transplantation in mice.

The mouse model of orthotopic corneal transplantation was used to evaluate the clinical course of corneal graft rejection process. Corneal grafts were placed into eyes of naive, unmodified recipients or recipients presensitized with skin graft two weeks before corneal transplantation. Two strain combinations were used, one with genetic disparity at both major and minor histocompatibility antigens and the other with the difference only at multiple minor histocompatibility antigens. A panel of syngeneic graft recipients served as controls. In naive recipients, rejection reaction was recorded in more than 90% of recipients mostly during the third week after grafting and 40-50% of corneas displayed irreversible failure in both strain combinations. Both MHC compatible and incompatible corneal grafts in all presensitized recipients were irreversibly rejected by a second-set allograft reaction. The results thus show an important role of multiple minor histocompatibility antigens in corneal allotransplantation in mice. In addition, the prompt reaction in presensitized recipients is evidence for expression of allotransplantation immunity in the eye, which has been for a long time considered as a privileged site sequestered from systemic immunity.