EVIDENCE THAT TREATMENT WITH DHRS9+ REGULATORY MACROPHAGES INDUCED BY FCγRIII LIGATION AND IFN-γ STIMULATION PROMOTES RENAL ALLOGRAFT TOLERANCE IN PATIENTS

Abstract

UNITED KINGDOM, 15 , Univ. Regensburg, Regensburg/GERMANY Although the adoptive transfer of allograft tolerance with suppressor cell populations is a common method in experimental Immunology, there remain substantial obstacles to clinical implementation of the technique. Self-evidently, any suppressor cell preparation intended for use as a tolerance-promoting therapy must be predictably efficacious and safe for the recipient which, in practical terms, means that the cells must be consistent in phenotype and function, and that their properties remain unaltered by administration. The human regulatory macrophage is a novel type of suppressor macrophage which may be a particularly suitable cell for promoting transplantation tolerance in the clinical setting because of its stable phenotype and T cellsuppressive activity. Human regulatory macrophages (M reg) arise when isolated CD14 + monocytes are cultivated in the presence of high concentrations of human serum for six days prior to maturation with IFN-γ. M regs are readily distinguished from macrophages in other activation states by their characteristic morphology and homogeneous CD14 -/low CD16 -/low CD80 -/low CD86 + HLA-DR int CD163 -TLR2 -TLR4 -cell surface phenotype. By raising monoclonal antibodies, DHRS9 was discovered to be a specific marker of M regs. Microarray analyses comparing M regs to a panel of differentially polarised macrophages confirmed the uniqueness and stability of the M reg phenotype, and identified CD258 (LIGHT) and CD85H (LILRA2) as additional M reg markers. Naturally-occurring DHRS9-expressing macrophages were detected in human spleen and we tentatively suggest that these represent physiological conterparts of the in vitro-derived M reg. It is thought that the M reg represents a committed state of macrophage differentiation and that its generation in vitro somehow recapitulates the in vivo development of tissue macrophages from CD16 + resident monocytes. Acquisition of the M reg phenotype by monocytes is a gradual process which depends upon plastic adherence and exposure to serum immunoglobulin. The M reg-inducing activity of immunoglobulin is attributed to signalling through Fc γ RIII and not Fc γ RIIb. M regs profoundly suppress mitogen-stimulated and alloantigen-driven T cell proliferation by deleting activated T cells. This suppressive activity of M regs has both a contact-dependent and contact-independent component; the latter can be partly attributed to the action of indoleamine 2,3-dioxygenase. Building on evidence from preclinical transplant studies that preoperative treatment with donor-derived M regs promotes allograft survival (abstract #2485) M regs were administered to two living-donor renal transplant recipients. Both patients were minimised to low-dose tacrolimus monotherapy within 24 weeks of transplantation and subsequently maintained excellent graft function. By one year, both patients displayed patterns of peripheral blood gene expression converging upon the IOT-RISET tolerance signature (J. Clin. Invest. 2010; 120(6):184...

In question: the scientific value of preclinical safety pharmacology and toxicology studies with cell-based therapies

“…In contrast, M regs upregulated CD16 expression within 1 day of infusion, which possibly reflects the absence of human immunoglobulins in NSG mice. 27 …”