Anti-CD2 monoclonal antibodies synergize with FK506 but not with cyclosporine or rapamycin to induce tolerance

Comparison between tacrolimus and cyclosporine as immunosuppressive agents compatible with tolerance induction by CD4/CD8 blockade

BACKGROUND

Donor-specific tolerance can be induced in mice by transient antibody blockade of the CD4 and CD8 co-receptors of T cells. To evaluate the potential application of CD4/CD8 blockade in the clinic, we have asked if either tacrolimus or cyclosporine counteract the tolerogenic process.

METHODS

Using the fully mismatched mouse cervical heart transplant model, BALB/c (H2d) to CBA (H2k), the experimental groups were (i) no therapy, (ii) tacrolimus (1 mg/kg, i.p., daily, days 0-14); (iii) cyclosporine (25 mg/kg, i.p., daily, days 0-14), (iv) blocking monoclonal antibodies (mAbs) to CD4 and CD8 (2 mg, i.p., starting day 0 and on alternating days thereafter for a total of six doses), (v) tacrolimus plus mAbs, and (vi) cyclosporine plus mAbs.

RESULTS

Allograft survival was prolonged in both the tacrolimus and cyclosporine groups. mAbs alone induced tolerance, and mAbs combined with tacrolimus also induced tolerance. In contrast, the combination of mAbs and cyclosporine was toxic.

CONCLUSIONS

The induction of tolerance by blocking CD4 and CD8 was not prevented by tacrolimus. However, combination of cyclosporine with the same tolerogenic protocol was toxic to mice.

Evaluation of the effect of interleukin-10 on the multiplication of Mycobacterium avium complex in human macrophages and in C57BL/6 mice

OBJECTIVE: To examine the effect of recombinant human IL-10 (rhIL-10) on MAC infection of human macrophages and C57BL/6 mice. METHODS: We compared rhIL-10 with the effects of the immunosuppressive drugs prednisolone and cyclosporin A, both in vitro and in vivo. RESULTS: There was no effect of rhIL-10 on the multiplication of MAC in human macrophages after 1 week of infection. In C57BL/6 mice, rhIL-10 at 2.5 or 25 m g/mouse had no additional multiplicatory effect after 3 weeks of infection, while the spleens of mice treated with prednisolone had 600% higher bacteria than controls or rhIL-10-treated mice (p0.01). CONCLUSIONS: These data suggest that rhIL-10 does not further decrease the resistance of human macrophages and C57BL/6 mice to MAC infection, whereas prednisolone leads to increased multiplication of MAC in the spleens of infected C57BL/6 mice. These results may be of interest in the context of the therapeutic use of rhIL-10 in some autoimmune disorders.

CD2 antigen targeting reduces intragraft expression of mRNA-encoding granzyme B and IL-10 and induces tolerance

We explored the hypothesis that CD2 antigen-specific therapy would reduce intragraft gene expression and facilitate the emergence of transplantation tolerance. This postulate was tested in a murine pancreatic islet cell allograft model in which a novel mAb directed at the CD2 antigen, RM2-2 anti-CD2 mAb (RM2-2 mAb), was used to regulate CD2 antigen-dependent antiallograft response. Peritransplant administration (day -1, 0, and day + 1 with respect to transplantation) of RM2-2 mAb resulted in significantly longer survival of DBA/2 pancreatic islet cell allografts in the B6AFl recipient compared with untreated recipients. RM2-2 mAb therapy facilitated the induction of antigen-specific tolerance: whereas retransplantation with the original donor strain (DBA/2) islet cell allograft was successful, retransplantation with a third-party donor (SJL) islet cell allograft was not. In vivo administration of RM2-2 mAb therapy resulted in a decrease in the percentage of T cells that coexpressed the CD2 antigen (demonstrated by two-color flow cytometry) and in a decrease in intragraft expression of cytotoxic cell specific granzyme B mRNA and IL-10 mRNA (detected by RT-PCR). Our data, in addition to demonstrating for the first time the efficacy of RM2-2 anti-CD2 mAb, suggest that CD2 antigen is a suitable target for the induction of transplantation tolerance.

The effect of combination splenectomy and low-dose FK506 therapy on graft survival after liver allograft transplantation in rats

The effect of splenectomy on allograft survival was investigated using orthotopic liver transplantation in a rat experimental model (ACI rat liver grafted to LEW rat). Control rats without any immunosuppressive treatment died, on average, 10.4 +/- 1.4 days after operation. Splenectomy alone somewhat prolonged the survival (13.4 +/- 2.0 days), and low-dose FK506 therapy moderately prolonged it (22.7 +/- 7 days). The graft survival period was significantly prolonged (39.7 +/- 6.3 days) when them two treatments were combined. The elevation of cytotoxic antiallograft antibodies was suppressed by splenectomy but not by low-dose FK506 therapy. The development of jaundice was moderately suppressed by FK506 but not by splenectomy. There was no difference between the pattern of body weight decline in either of them two groups and that in control rats. When these two treatments were combined at the same time, the elevation of cytotoxic antibodies, development of jaundice and decline of body weight were suppressed. These data indicate that B cells play an important role in the acute rejection of the rat liver allograft at least partially via production of cytotoxic antiallograft antibody. Splenectomy or other immunosuppressive methods affecting B cells can be a supplement for immunosuppression when using reduced-dose FK506.

Immunotolerance and prevention of ocular autoimmune disease

Immunotherapeutic approaches to autoimmune disease have a common goal of inducing antigen-specific, long-lasting tolerance to autoantigens, without otherwise compromising the immune response. Here we review some of the most interesting experimental advances in this area. We discuss the use of T cell targeting drugs that have been reported to induce long lasting tolerance to ocular antigens. Strategies involving the targeting of idiotypic and clonotypic determinants associated with ocular autoimmunity, such as idiotypic network manipulation and T cell vaccination, are reviewed. The use of cytokines to promote perturbation of the Th1/Th2 balance with its possible implications for treatment of uveitis, is analysed. Finally, we review tolerogenic strategies based on acquisition of tolerance following presentation of antigen through alternative routes, such as injection of antigen into the anterior chamber, intravenous infusion of antigen, and oral administration of retinal antigens. Special emphasis is placed on the last strategy, since there are ongoing clinical trials using oral tolerance as an immunotherapeutic approach to treat autoimmune diseases, among them uveitis.