Immunoglobulin-Like Transcript 3-Fc Suppresses T-Cell Responses to Allogeneic Human Islet Transplants in hu-NOD/SCID Mice

Abstract

OBJECTIVE-The aim of our study was to explore the immunomodulatory activity of soluble immunoglobulin (Ig)-like transcript (ILT) 3-Fc in pancreatic islet transplantation and to determine its mechanism of action.RESEARCH DESIGN AND METHODS-NOD/SCID mice in which diabetes was induced by streptozotocin injection were transplanted with human pancreatic islet cells. Mice in which the transplant restored euglycemia were humanized with allogeneic peripheral blood mononuclear cells and treated with ILT3-Fc or control human IgG or left untreated. The blood glucose level was monitored twice a week, and rejection was diagnosed after two consecutive readings Ͼ350 mg/dl. Tolerated and rejected grafts were studied histologically and by immunostaining for human T-cells and insulin production. CD4 and CD8 T-cells from the spleen were studied for suppressor activity, expression of cytokines, and CD40L. RESULTS-Although human T-cell engraftment was similar inall groups, ILT3-Fc-treated mice tolerated the islets for the entire period of observation (91 days), whereas control mice rejected the graft within 7 weeks (P Ͻ 0.0001). ILT3-Fc treatment suppressed the expression of cytokines and CD40L and induced the differentiation of human CD8 ϩ T suppressor cells that inhibited Th alloreactivity against graft HLA antigens. T-cells allostimulated in vitro in the presence of ILT3-Fc inhibited CD40L-induced upregulation of CD40 in human pancreatic islet cells. Histochemical studies showed dramatic differences between human pancreatic islets from tolerant, ILT3-Fc-treated mice and control recipients rejecting the grafts.CONCLUSIONS-The data indicated that ILT3-Fc is a potent immunoregulatory agent that suppressed islet allograft rejection in humanized NOD/SCID mice.

Downregulation of Inflammatory MicroRNAs by Ig-like Transcript 3 Is Essential for the Differentiation of Human CD8+ T Suppressor Cells

“…ILT3Fc-induced inhibition of IFN-g expression was found in all of our previous studies (9)(10)(11)(12) and is shown as a control for the ILT3Fc effect ( Fig. 2A).…”

“…The strong immunosuppressive activity of ILT3Fc has been documented by its ability to suppress allograft rejection (10,11), a phenomenon in which myriads of MHC-bound peptides are recognized via the direct and indirect pathways, triggering rejection (45). Therefore, it is most likely that recognition of a limited number of autoantigenic, tissue-specific peptides can be inhibited by ILT3Fc.…”

“…This recombinant protein inhibited primary and secondary T cell responses in MLC and blocked the differentiation of CD8 + cytotoxic T cells (CTL). Furthermore, it elicited the in vitro and in vivo differentiation of CD8 + Ts, which produced no cytokines, inhibited T cell reactivity and induced the upregulation of ILT3 on priming APC (9)(10)(11). In vivo studies showed that ILT3Fc induced tolerance to allogeneic human pancreatic islet cells transplanted in humanized diabetic NOD/SCID mice (10, 11).…”

Regulation of T‐cell immunity by leucocyte immunoglobulin‐like receptors: innate immune receptors for self on antigen‐presenting cells

“…15,16 In contrast, at least some of the inhibitory effects of LILRB4 may result from 'reverse signalling' through its T-cell ligand, as soluble forms of the receptor are sufficient to inhibit T-cell proliferation. 17,18 As evidenced by their nomenclature, LILRA2 and LIL-RA4 signal through ITAM motifs and might therefore be expected to exert 'activating' effects on the APC phenotype. Instead, LILRA4 negatively regulates the secretion of type I interferons by plasmacytoid DCs.…”

“…LILRA2 engagement Involved in HLA-G-mediated allograft tolerance 49,94 Peripheral blood mononuclear cells from patients with systemic lupus erythematosus exhibit poor LILRB1 function and diminished expression of this receptor on B cells 58 Coexpressed with HLA-G in multiple sclerosis lesions 60 Up-regulated during HIV infection (see text for details) 63,64,95,96 Proportion of LILRB1 + B cells correlates with severity of malaria 70 Involved in HLA-G-mediated tumour immune evasion 38,[75][76][77]79 LILRB2 Up-regulated on DCs and ECs in the T-cell suppression cascade which generates allograft tolerance 13,23,41 Involved in HLA-G-mediated allograft tolerance 48,94 Up-regulated in rheumatoid arthritis, suggested role in spondyloarthritis 51,53 Up-regulated by interleukin-10 in HIV patients 27 Higher affinity for HIV-1 viral escape mutant 15 Expressed on B cells in leukaemia patients and tumour cells in lung cancer patients 72,73 Involved in HLA-G-mediated tumour immune evasion 38,[75][76][77]79 LILRB4 Up-regulated on DCs and ECs in the T-cell suppression cascade which generates allograft tolerance 13,23,41 Suppresses pancreatic islet allograft rejection in humanized NOD/SCID mice 17 Role in tumour cell evasion of host immune system 18,71 Expressed on B cells in leukaemia patients 72 DCs, dendritic cells; ECs, endothelial cells; HCMV, human cytomegalovirus; HIV, human immunodeficiency virus; HLA, human leucocy...…”