Heme oxygenase-1 end-products carbon monoxide and biliverdin ameliorate murine collagen induced arthritis.

OBJECTIVES: Heme oxygenase-1 (HO-1) which degrades Heme to free iron, biliverdin and carbon monoxide (CO) plays an important role in inflammation. There are, however, conflicting data concerning the role of HO-1 in rheumatoid arthritis (RA) and the therapeutic potential of individual heme degradation products remains to be determined. We therefore investigated the effect of CO and biliverdin upon therapeutic administration in the murine collagen induced arthritis (CIA) model of RA. METHODS: CIA was induced in DBA/1 mice. Anti-CII antibody levels were determined by ELISA. Mice were scored for paw swelling and grip strength. After the first clinical signs of arthritis one group of animals was treated with biliverdin, the second group was treated with CO. After 60 days all animals were sacrificed and analysed for histomorphological signs of arthritis. RESULTS: All animals immunised with CII developed serum anti-CII antibodies. Antibody levels were decreased in the CO-treated group. Both, Biliverdin and the CO-treated animals, showed an improvement in clinical disease activity. Histological analysis revealed significantly less inflammation, erosion and reduced numbers of osteoclasts in CO-treated animals only, whereas cartilage degradation was prevented in both biliverdin and CO-treated animals. CONCLUSIONS: Our data demonstrate a beneficial effect of CO, in particular, and biliverdin, on inflammation and bone destruction in the CIA mouse model.

Accommodation of vascularized xenografts: expression of "protective genes" by donor endothelial cells in a host Th2 cytokine environment.

Organ xenografts under certain circumstances survive in the presence of anti-graft antibodies and complement, a situation referred to as "accommodation." We find that the endothelial cells (ECs) in hamster hearts that accommodate themselves in rats express genes, such as A20 and bcl-2, that in vitro protect ECs from apoptosis and prevent upregulation in those cells of proinflammatory genes such as cytokines, procoagulant and adhesion molecules. Hearts that are rejected do not express these genes. In addition, vessels of rejected hearts show florid transplant arteriosclerosis whereas those of accommodated hearts do not. Accommodated xenografts have an ongoing T helper cell type 2 (Th2) cytokine immune response, whereas the rejected grafts have a Th1 response. We propose a model for factors that contribute to the survival of xenografts and the avoidance of transplant arteriosclerosis.

Carbon monoxide has anti-inflammatory effects involving the mitogen-activated protein kinase pathway.

The stress-inducible protein heme oxygenase-1 provides protection against oxidative stress. The anti-inflammatory properties of heme oxygenase-1 may serve as a basis for this cytoprotection. We demonstrate here that carbon monoxide, a by-product of heme catabolism by heme oxygenase, mediates potent anti-inflammatory effects. Both in vivo and in vitro, carbon monoxide at low concentrations differentially and selectively inhibited the expression of lipopolysaccharide-induced pro-inflammatory cytokines tumor necrosis factor-alpha, interleukin-1beta, and macrophage inflammatory protein-1beta and increased the lipopolysaccharide-induced expression of the anti-inflammatory cytokine interleukin-10. Carbon monoxide mediated these anti-inflammatory effects not through a guanylyl cyclase-cGMP or nitric oxide pathway, but instead through a pathway involving the mitogen-activated protein kinases. These data indicate the possibility that carbon monoxide may have an important protective function in inflammatory disease states and thus has potential therapeutic uses.

Expression of heme oxygenase-1 can determine cardiac xenograft survival.

The rejection of concordant xenografts, such as mouse-to-rat cardiac xenografts, is very similar to the delayed rejection of porcine-to-primate discordant xenografts. In concordant models, this type of rejection is prevented by brief complement inhibition by cobra venom factor (CVF) and sustained T-cell immunosuppression by cyclosporin A (CyA). Mouse hearts that survive indefinitely in rats treated with CVF plus CyA express the anti-inflammatory gene heme oxygenase-1 (HO-1) in their endothelial cells and smooth muscle cells. The anti-inflammatory properties of HO-1 are thought to rely on the ability of this enzyme to degrade heme and generate bilirubin, free iron and carbon monoxide. Bilirubin is a potent anti-oxidant, free iron upregulates the transcription of the cytoprotective gene, ferritin, and carbon monoxide is thought to be essential in regulating vascular relaxation in a manner similar to nitric oxide. We show here that the expression of the HO-1 gene is functionally associated with xenograft survival, and that rapid expression of HO-1 in cardiac xenografts can be essential to ensure long-term xenograft survival.

I-N: a newly described H-2 I subregion between K and I-A.

Strong, primary mixed leukocyte culture-proliferative responses in certain K region-incompatible strain combinations led us to consider whether an I region-like locus might exist between K and I-A. Results obtained with an (A. TL X B10.D2)F1 anti-B10.BR serum provided serological evidence for a new locus; B10.T(6R)-absorbed serum retained reactivity on AQR lymphocytes. This finding demonstrates an antigen, Ia.W41, encoded by a locus, Ia-7, within a new I subregion, I-N.

Generation of primary cytotoxic lymphocytes against non-major histocompatibility complex antigens by anti-Ia serum plus complement-treated lymphocytes.

The results presented in this paper demonstrate that responding cells that remain after anti-Ia serum plus complement (C) treatment generate a highly significant in vitro cytotoxic response against minor histocompatibility complex antigens. The cytotoxic response appears to be antigen specific in that target cells of strains other than the sensitizing strain are not lysed, or lysed to a lesser extent. The cytotoxic cells are susceptible to anti-Thy-1 plus C lysis. Anti-Ia serum may function by removing an unprimed suppressor cell, although other mechanisms cannot be ruled out.

Quantitative assay of antigenic disparity at hl-a-the major histocompatibility locus in man.

We have extended the method of one-way stimulation in mixed leukocyte culture tests as previously described to quantitate different degrees of stimulation. To demonstrate that the amount of stimulation is immunogenetically meaningful, siblings and parents in families in whom genotyping on the basis of leukocyte antigen data was possible were tested. The prediction that cells of siblings differing from the responding sibling by both alleles at HL-A, stimulate more than do cells of siblings differing by only one allele, was realized in every case. One exception, with cells of a parent, is discussed. It is stressed that the differences measured here are probably fairly strong ones in the majority of cases, and that lesser differences cannot yet be detected reproducibly.

Phenotypic expressions of the major histocompatibility locus in man (HL-A): leukocyte antigens and mixed leukocyte culture reactivity.

The evidence is reviewed that a single genetic system, the major histocompatibility locus in man, HL-A, determines most of the antigens measured by presently available leukocyte isoantisera, and also controls reactivity in one-way mixed leucocyte culture tests. Studies in 12 families are presented to support this conclusion. Some interesting exceptions to the general typing-MLC tests correlation are presented and discussed.

Alternative pathways of T lymphocyte activation.

Data presented in this paper suggest that there may be two alternative pathways which T lymphocytes can use in generating a cytotoxic response to alloantigens in vitro. First, there is the pathway taken when stimulator and responder cells differ by an entire H-2 complex where Ly1+2- helper T lymphocytes respond to I region encoded lymphocyte defined differences and provide help to the Ly1-2+ cytotoxic T lymphocytes responsive primarily to K/D region encoded cytotoxicity defined determinants. Second, there is the pathway taken when stimulator and responder cells differ by only K or D region differences without an I region encoded difference; under these conditions, an Ly1+2+ cell, which does not appear to play a significant role in the development of a cytotoxic response to an entire H-2 difference, appears to play a pivotal role.

In vitro sensitization of thymocytes. Role of H-21 I region determinants and cell-free mixed leukocyte culture supernates in generation of cytotoxic responses.

Stimulation of thymocytes in vitro by spleen cells differing for the entire H-2 complex leads to a significant proliferative response without a significant cell-mediated lympholysis (CML) response. Addition of soluble cell-free supernates (SF), (taken from a 7-day mixed leukocyte culture) enables these cultures to develop CML response. For optimal CML response, the SF has to be added within 48 h of onset of cultures. Although with spleen cells as responding cells, SF could quantitatively replace I-region different stimulating cells for generation of CML responses, with thymocytes as responding cells, stimulation with I-region cells appeared obligatory for the generation of CML responses. The implications of these findings are discussed.

T-cell-specific murine Ia antigens: serology of I-J and I-E subregion specificities.

(B10 X B10.D2)F1 mice were immunized with B10.A(5R) concanavalin A-stimulated thymocyte blasts. The genetic disparity between donor and recipient was restricted to the I-J and I-E subregions of the murine major histocompatibility (H-2) complex. A high-titered, T-cell-specific anti I-JkEk serum was obtained. The antiserum lysed 27-30% of haplotype k, q, or s lymph node cells, 5.3 +/- 2% of haplotype k spleen cells, and did not lyse thymocytes. Nylon wool-passed lymph node or spleen cells (H-2k) showed considerable reactivity with anti-I-JkEk serum (35-40% lysis); anti-Thy1.2 plus complement-treated spleen cells did not react (less than 5% lysis). I-Ek antibody was detected by B10.A(3R) lymph node cell reactivity (20% lysis), whereas reaction with H-2k lymph node cells after B10.A(3R) absorption demonstrated IJk antibody (12% lysis). Lymphocyte activation with alloantigen or mitogen led to increased anti-I-JkEk serum reactivity. These results, showing antibody production to at least two T-cell Ia antigenic determinants by concanavalin A thmocyte blast immunization, suggest that a group of I-region-encoded T-cell specificities may not have been detected using conventional immunization protocols because they would not have comprised a major antigenic component of the immunizing cell population. The existence of multiple Ia antigenic determinants unique to T lymphocytes would have important implications for serological and functional studies of T-cell subpopulations.

Involvement of fusion activity of ultraviolet light-inactivated Sendai virus in formation of target antigens recognized by cytotoxic T cells.

Mice inoculated with ultraviolet light-inactivated Sendai virus mount a cell- mediated immune response to the virus. Cytotoxic T cells specific for Sendai virus can be obtained by in vitro secondary stimulation of primed spleen cells with syngeneic stimulator cells coated with UV-inactivated Sendai virus. Neither in vivo nor in vitro stimulation alone is sufficient to generate specific cytotoxic T cells. Sharing of the H-2 haplotype between cytotoxic T cells and target cells is required for the Sendai virus-specific lysis to occur. The fusion (F) glycoprotein of Sendai virus has been implicated in target antigen formation (20). Ethanol treatment of Sendai virus causes complete inactivation of the cell-fusion and hemolytic activities of the envelope, but does not affect the antigenicity of the F glycoprotein; furthermore, hemagglutinin and neuraminidase activities of the envelope HANA glycoprotein are also left intact after ethanol treatment. Target cells can be prepared by coating them with various numbers of UV-inactivated Sendai virus that have been treated with ethanol or, as a control, phosphate-buffered saline (PBS). The amount of virus adsorbed to target cells during the cytotoxicity reaction time using either ethanol-treated or untreated (PBS "treated") virions is essentially identical, but target cells coated with ethanol-treated Sendai virus fail to serve as targets for cytotoxic T cells. These results indicate that fusion activity of the Sendai virus envelope is essential to the formation of the target antigen and that virus adsorption to cell surfaces without fusion of the envelope with cell membranes is not sufficient to allow killing by virus-specific cytotoxic T cells.

H-2 I-region encoded targets in allograft rejection.

Fresh thyroids transplanted to I-region disparate recipients are, in most cases, rejected; in some instances fresh thyroids undergo periods of crisis followed by functional recovery. Cultured thyroids that are taken from donor animals pretreated with lymphocytotoxic drugs, gamma radiation and cultured for 10 d in vitro are not rejected by any normal allogenic recipient. If the recipient is sensitized with lymphoid cells syngeneic with an I-region disparate cultured thyroid donor, the cultured thyroid is rejected if I-A-subregion differences are included. We interpret these data to indicate that there exist I-region encoded perenchymal cell target determinants which are not, by themselves, immunogenic.

Cellular basis of neonatal induction of in vitro tolerance.

The LD and SD antigens of the major histocompatibility complex subserve differential roles in the induction of the proliferative phase in mixed lymphocyte culture and in the cytotoxic reaction seen in cell-mediated lympholysis. The present study suggests that they also behave differently in the neonatal induction of tolerance. SD antigens appear to induce tolerance in the cytotoxic T lymphocytes very effectively, whereas LD antigens (or the cytotoxic targets coded by genes in the I and/or S regions) are relatively ineffective in this regard. LD antigens presented neonatally are effective at inducing tolerance in the proliferating helper cells.

Cell-mediated immunity: differential maturation of mixed leukocyte reaction and cell-mediated lympholysis.

While spleen cells from neonatal B10 (H-2b) are reactive (proliferate) in one-way mixed leukocyte culture, cell-mediated lympholysis reactivity does not arise until 7 days of age. When B10 cells are sensitized to B10.D2 (H-2d), cross-killing of third-party B10.BR (H-2k) target is always lower than the specific killing of B10.D2 targets and is not demonstrable until 27 days after birth.

Allogeneic and xenogeneic response in mixed leukocyte cultures.

The mixed lymphocyte culture (MLC) test has been regarded as an in vitro model of the recognition or sensitization phase of the homograft or graft-versus-host reaction. It has been suggested that the graft-versus-host response in vivo is less in xenogeneic combinations than in allogeneic ones and that there is a similar quantitative relationship in MLC responses. Given the above interpretation of the MLC test, this could suggest that the lesser reactivity in xenogeneic combinations may be due to a lesser recognition of the stimulus. We have done nine experiments testing allogeneic and xenogeneic combinations in MLC, largely in combinatorial fashion. The results indicate that the response in xenogeneic MLC may be as great as that in allogeneic MLC and that, as in different allogeneic mixtures, there is great variation in the extent to which xenogeneic mixtures may respond.

Role of H-2 lymphocyte-defined and serologically-defined components in the generation of cytotoxic lymphocytes.

The cell-mediated lympholytic capability of mouse spleen cells stimulated in mixed lymphocyte culture is determined by lymphocyte-defined (LD) and serologically-defined (SD) antigenic differences present during sensitization. Cells which are activated by LD differences alone are markedly less effective in causing lysis of target cells. This lack of cytotoxicity is shown to be, at least in part, due to the inability of LD differences to allow the efficient generation of cytotoxic lymphocytes. SD antigens not only serve as good targets for CML but are also shown to be important for the generation of cytotoxic lymphocytes during the mixed lymphocyte culture.

Genetic control of cell-mediated lympholysis in mouse.

H-2 congenic mouse strains were tested in vitro to investigate the genetic control of cell-mediated lympholysis (CML). Combinations were selected such that differences in various segments of H-2 could be examined for their ability to stimulate production of effector cells and to serve as targets for lysis. Particular emphasis was directed towards understanding the roles of LD and SD. SD-region differences are important in the sensitization of effector cells and they also function as strong targets for lysis, or as markers for the CML targets. LD differences are also important for sensitization of cytotoxic effector cells, but they serve only as very weak targets for lysis. Collaboration occurs between LD and SD in generation of CML. The nature of this interaction can be of two types: together LD and SD can produce CML which neither difference alone can stimulate; LD can enhance a CML response stimulated by SD-region differences alone.

Cellular basis of the proliferative response of human T cells to mouse xenoantigens.

Purified human T cells respond proliferatively to allogenic peripheral blood mononuclear (PBMC) stimulating cells but show no response to murine splenic stimulating cells. Two possible explanations for the lack of xenogeneic response are that human T cells, educated in a human thymus, cannot directly recognize a molecule as disparate as mouse antigen encoded by H-2 and/or that a cytokine(s) produced by the APCs is needed to allow a proliferative response and that the cytokine(s) produced by murine APC do not provide an adequate stimulus to the human T cells under these conditions. We show here that highly purified human T cells can respond directly in an antigen-specific manner to murine stimulating cells if human rIL-1 or rIL-2 or a T cell growth factor (TCGF) preparation are present in the culture. These findings demonstrate that human T cells can recognize murine antigens and that a highly significant response can be obtained if a human cytokine is present to permit that response.

Recognitive specificity of human cytotoxic T lymphocytes. I. Antigen-specific inhibition of human cell-mediated lympholysis.

The specificity of antigen recognition by in vitro sensitized human cytotoxic T lymphocytes (CTLs) has been studied using a sensitive cell-mediated lympholysis (CML) assay. Frequently, high levels of cytotoxicity are observed on third-party targets unrelated to sensitizing or responding cells; however, no cytotoxicity differing significantly from zero has been observed on targets autologous to the responding CTLs. This "cross-killing" of third-party target cells has been observed when stimulating and third-party cells bear no cross-reacting serologically defined (SD) antigens, thought to be the target antigens recognized by CTLs. CML-blocking studies, using unlabeled normal human lymphocytes to inhibit 51Cr release from radiolabeled target cells, have shown that cross-killing, even in the absence of shared SD determinants, results from CTLs recognizing antigens shared by the third-party targets and the initial stimulating population. Furthermore, these antigens have been mapped to the major histocompatibility complex (MHC). The ability of human CTLs to specifically recognize MHC-controlled antigens not detected serologically suggests that SD antigens may be recognized differently by alloantisera and CTLs, or that MHC antigens other than SD may be the targets of CTLs in CML.