ABSTRACT
Although xenografts are one of the most attractive strategies for overcoming the shortage of organ donors, cellular rejection by macrophages is a substantial impediment to this procedure. It is well known that macrophages mediate robust immune responses in xenografts. Macrophages also express various inhibitory receptors that regulate their immunological function. Recent studies have shown that the overexpression of inhibitory ligands on porcine target cells results in the phosphorylation of tyrosine residues on intracellular immunoreceptor tyrosine-based inhibitory motifs on macrophages, leading to the suppression of xenogenic rejection by macrophages. It has also been reported that myeloid-derived suppressor cells, a heterogeneous population of immature myeloid cells, suppress not only NK and cytotoxic T lymphocyte cytotoxicity but also macrophage-mediated cytotoxicity. This review is focused on the recent findings regarding strategies for inhibiting xenogenic rejection by macrophages.
Subject(s)
Graft Rejection/prevention & control , Graft Survival , Immunity, Cellular , Macrophages/immunology , Transplantation, Heterologous/adverse effects , Animals , CD47 Antigen/genetics , CD47 Antigen/immunology , CD47 Antigen/metabolism , Graft Rejection/genetics , Graft Rejection/immunology , Graft Rejection/metabolism , Heterografts/immunology , Histocompatibility Antigens Class I/genetics , Histocompatibility Antigens Class I/immunology , Histocompatibility Antigens Class I/metabolism , Humans , Killer Cells, Natural/immunology , Killer Cells, Natural/metabolism , Macrophages/metabolism , Myeloid-Derived Suppressor Cells/immunology , Myeloid-Derived Suppressor Cells/metabolism , Myeloid-Derived Suppressor Cells/transplantation , Phagocytosis , Pulmonary Surfactant-Associated Protein D/genetics , Pulmonary Surfactant-Associated Protein D/immunology , Pulmonary Surfactant-Associated Protein D/metabolism , Sialyltransferases/genetics , Sialyltransferases/immunology , Sialyltransferases/metabolism , Signal Transduction , Treatment Outcome , beta-D-Galactoside alpha 2-6-SialyltransferaseABSTRACT
Juvenile myelomonocytic leukemia (JMML) is a myeloproliferative neoplasm (MPN) of childhood with a poor prognosis. Mutations in NF1, NRAS, KRAS, PTPN11 or CBL occur in 85% of patients, yet there are currently no risk stratification algorithms capable of predicting which patients will be refractory to conventional treatment and could therefore be candidates for experimental therapies. In addition, few molecular pathways aside from the RAS-MAPK pathway have been identified that could serve as the basis for such novel therapeutic strategies. We therefore sought to genomically characterize serial samples from patients at diagnosis through relapse and transformation to acute myeloid leukemia to expand knowledge of the mutational spectrum in JMML. We identified recurrent mutations in genes involved in signal transduction, splicing, Polycomb repressive complex 2 (PRC2) and transcription. Notably, the number of somatic alterations present at diagnosis appears to be the major determinant of outcome.
Subject(s)
Genetic Predisposition to Disease/genetics , Genome-Wide Association Study/methods , Leukemia, Myelomonocytic, Juvenile/genetics , Mutation , Signal Transduction/genetics , Acute Disease , Child , Child, Preschool , DNA Copy Number Variations , Disease Progression , Disease-Free Survival , Female , High-Throughput Nucleotide Sequencing/methods , Humans , Infant , Leukemia, Myeloid/diagnosis , Leukemia, Myeloid/genetics , Leukemia, Myelomonocytic, Juvenile/diagnosis , Male , PrognosisABSTRACT
BACKGROUND: Xenotransplantation is an appealing alternative to human allotransplantation because of a worldwide shortage of organs. One of the obstacles for xenografts is cellular rejection by the innate immune system, comprised of NK cells, monocytes, and macrophages. In this study the inhibitory function of HLA-G1, a MHC Ib molecule, on macrophage-mediated cytotoxicity was examined. Furthermore, this study also evaluates the suppressive effect of cytokine production by macrophages. METHODS: The expression of inhibitory receptors that interact with HLA-G1, immunoglobulin-like transcript 2 (ILT2), ILT4 and KIR2DL4 (CD158d) on in vitro generated macrophages were examined by flow cytometry. Complementary DNA (cDNA) of HLA-G1, HLA-E and human ß2-microglobulin (hß2m) were prepared and transfected into swine endothelial cells (SECs). The expression of the transgenic genes was evaluated by flow cytometry, and macrophage-mediated SEC cytolysis was assessed using the macrophages. RESULTS: In vitro generated macrophages expressed not only ILT2 and ILT4 but CD158d as well. The transgenic HLA-G1 on SECs indicated significant suppression in macrophage-mediated cytotoxicity, which was equivalent to that of transgenic HLA-E. Furthermore, the results on real time PCR and ELISA revealed that transgenic HLA-G1 induces the anti-inflammatory cytokines, such as IL-10 and TGF-ß, and suppresses iNOS mRNA expression, indicating that transgenic HLA-G1 has suppressive effects in a broad range of transplant rejection. CONCLUSION: These results indicate that generating HLA-G1 transgenic pigs can protect porcine grafts from macrophage-mediated cytotoxicity.