Roland Buelow

Stress protein-induced immunosuppression: inhibition of cellular immune effector functions following overexpression of haem oxygenase (HSP 32)

This is the first report on suppression of immune effector functions following upregulation of heat shock protein 32 (HSP 32), known as haem oxygenase (HO-1). Here we evaluated the effect of cobalt-protoporphyrin (CoPP)-induced HO-1 expression on cell-mediated immune responses. Administration of CoPP to CBA mice resulted in overexpression of HO-1 in the spleen, liver and kidneys. In vitro measurements of T cell-mediated and NK-cell-mediated cytotoxicity in spleens from CoPP-treated animals demonstrated a severe suppression of their effector functions while administration of Zn-PP or vitamin B12 had no effect. Furthermore, CoPP therapy decreased the lymphoproliferative alloresponse and differentiation of cytotoxic T cells. Inhibition of proliferation appeared to be due to cell growth arrest with an increased number of cells staying in G0/G1 phase. Despite the suppressed proliferative response, IL-2 production in the MLR was not inhibited. In contrast, CoPP decreased the production of IL-10, IFN-gamma and TNF-alpha. In vivo, CoPP prolonged the survival of heterotopic heart allografts in mice. The immunosuppressive effects following CoPP-mediated upregulation of HO-1 were similar to those observed after peptide-mediated upregulation of HO-1. The results indicate that overexpression of HO results in the inhibition of several immune effector functions and thus provides an explanation for stress-induced immunosuppression.

Peritransplant treatment with cobalt protoporphyrin attenuates chronic renal allograft rejection.

Allogen‐independent injury contributes to chronic rejection in renal allografts and heme oxygenase‐1 (HO‐1) has been shown to be protective in a number of settings. This study evaluated the effect of renal allograft recipient HO‐1 up‐regulation on chronic rejection in a rat model. Rat (F344 to Lewis) renal transplantation recipients were grouped: (i) cyclosporine (CsA) alone (0.75u2003mg/kg s.c.u2003×u200310u2003day; nu2003=u20035); (ii) CsAu2003+u2003low dose cobalt protoporphyrin (CoPP) an HO‐1 inducer (0.5u2003mg/kg i.p. on days −5,0,5; nu2003=u200313) and (iii) CsAu2003+u2003high dose CoPP (5.0u2003mg/kg i.p. on days −5,0,5; nu2003=u20038). Renal function was assessed by serum creatinine levels on day 140. Histopathologic changes in allografts were graded. Morphometric analyses performed to objectively quantify the vascular changes and glomerulosclerosis. HO‐1 expression quantified by Western blot and both HO‐1 and endothelin (ET‐1) localized using immunohistochemistry. Recipients treated with CsAu2003+u2003high dose CoPP had significantly decreased cortical scarring, vascular hyalinization and intimal thickness. They also had a significant, dose dependant, reduction in luminal obliteration and glomerulosclerosis by morphometric analyses. This freedom from chronic rejection in recipients treated with CoPP translated into quiescent grafts at postoperative day 140 with immunostaining and Western blot demonstrating decreased level of HO‐1 versus controls (Pu2003=u20030.012). In summary, the peritransplant up‐regulation of HO‐1 in renal allograft recipients significantly attenuates chronic rejection in rat renal allografts by inhibiting transplant vasculopathy.

Monoclonal antibody to the HLA class I α3 domain inhibits T cell activation and prolongs cardiac allograft survival in HLA— transgenic mice

Antibodies recognizing MHC class I molecules expressed on the surface of T cells have been shown to inhibit T cell responses in vitro. These findings suggested that therapy with such an antibody may prevent rejection and promote graft acceptance. We therefore tested the effect of an anti-HLA class I alpha 3 domain antibody (TP25.99) in vivo using transgenic C57BL/6 mice expressing HLA-B2705. Flow cytometric analysis confirmed the binding of TP25.99 to normal human peripheral blood lymphocytes and to mouse spleen cells, bone marrow cells and thymocytes isolated from hemizygous (+/-) transgenic littermates but not from homozygous (-/-) littermates. TP25.99 inhibited OKT-3-induced, but not PMA+ionomycin-induced, proliferation of human peripheral blood lymphocyte as well as anti-CD3 or Con A-induced proliferation of HLA+ mouse T cells. Both intact monoclonal antibody TP25.99 and TP25.99 Fab inhibited T cell proliferation. Reduced proliferation was associated with suppressed production of interleukin-2 as measured by ELISA. The efficacy of TP25.99 Fab in vivo was evaluated in a heart allograft model. Antibody therapy of (H-2h, B2705+) transgenic recipients of allogeneic Balb/c (H-2d) heart grafts prolonged graft survival significantly (MST = 19.8 +/- 6.4, p = 0.003) compared to treated (H-2b, B2705-) (MST = 9.17 +/- 2.2) or untreated (H-2b, B2705+) (MST = 10.0 +/- 2.8) transgenic recipients. This demonstrates that immunomodulation through anti-HLA class I antibody therapy can lead to prolongation of graft survival.