Axl, a member of the TAM (Tyro3, Axl, Mer) family of receptor tyrosine kinases, displays an increasingly important role in carcinogenesis. Analysis of 58 cutaneous melanoma lines indicated that Axl was expressed in 38% of them, with significant overrepresentation in NRAS- compared with BRAF-mutated tumors. Axl activation could be induced by autocrine production of its ligand, Gas6, in a significant fraction of Axl-positive tumors. Pearson's correlation analysis on expression data from five data sets of melanoma lines identified several transcripts correlating positively or negatively with Axl. By functionally grouping genes, those inversely correlated were involved in melanocyte development and pigmentation, whereas those positively correlated were involved in motility, invasion, and microenvironment interactions. Accordingly, Axl-positive melanomas did not express microphthalmia transcription factor (MITF) and melanocyte differentiation antigens (MDAs) such as MART-1 and gp100 and possessed a greater in vitro invasive potential compared with Axl-negative ones. Motility, invasivity, and ability to heal a wound or to migrate across an endothelial barrier were inhibited in vitro by Axl knockdown. Pharmacological inhibition of Axl using the selective inhibitor R428 had comparable effects in reducing migration and invasion. These results suggest that targeted inhibition of Axl signaling in the subset of melanomas lacking MITF and MDAs may represent a novel therapeutic strategy.

Autoreactive CD4(+) T cells are an essential feature of type 1 diabetes mellitus. We applied single-cell TCR α- and β-chain sequencing to peripheral blood GAD65-specific CD4(+) T cells, and TCR α-chain next-generation sequencing to bulk memory CD4(+) T cells to provide insight into TCR diversity in autoimmune diabetes mellitus. TCRs obtained for 1650 GAD65-specific CD4(+) T cells isolated from GAD65 proliferation assays and/or GAD65 557I tetramer staining in 6 patients and 10 islet autoantibody-positive children showed large diversity with 1003 different TCRs identified. TRAV and TRBV gene usage was broad, and the TRBV5.1 gene was most prominent within the GAD65 557I tetramer(+) cells. Limited overlap (<5%) was observed between TCRs of GAD65-proliferating and GAD65 557I tetramer(+) CD4(+) T cells. Few TCRs were repeatedly found in GAD65-specific cells at different time points from individual patients, and none was seen in more than one subject. However, single chains were often shared between patients and used in combination with different second chains. Next-generation sequencing revealed a wide frequency range (<0.00001-1.62%) of TCR α-chains corresponding to GAD65-specific T cells. The findings support minor selection of genes and TCRs for GAD65-specific T cells, but fail to provide strong support for TCR-targeted therapies.

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Aims/hypothesis Autoantibodies against pancreatic islets and infections by enteroviruses are associated with type 1 diabetes, but the specificity of immune responses within the type 1 diabetic pancreas is poorly characterised. We investigated whether pancreatic lymph nodes could provide a source of antigen-specific B cells for analysis of immune responses within the (pre)diabetic pancreas. Methods Human IgG antibodies were cloned from single B lymphocytes sorted from pancreatic lymph node cells of three organ donors positive for islet autoantibodies, and from the peripheral blood of a patient with type 1 diabetes. Antibodies to insulinoma-associated antigen 2 (IA-2), GAD65, zinc transporter 8 (ZnT8) and Coxsackie B virus proteins were assayed by immunoprecipitation and by immunofluorescence on pancreatic sections. Results Human IgG antibodies (863) were successfully cloned and produced from 4,092 single B cells from lymph nodes and peripheral blood. Reactivity to the protein tyrosine phosphatase domain of the IA-2 autoantigen was detected in two cloned antibodies: one derived from a pancreatic lymph node and one from peripheral blood. Epitopes for these two antibodies were similar to each other and to those for circulating antibodies in type 1 diabetes. The remaining 861 antibodies were negative for reactivity to IA-2, GAD65 or ZnT8 by both assays tested. Reactivity to a Coxsackie viral protein 2 was detected in one antibody derived from a peripheral blood B cell, but not from lymph nodes. Conclusions/interpretation We show evidence for the infrequent presence of autoantigen-specific IgG + B lymphocytes in the pancreatic-draining lymph nodes of islet autoantibodypositive individuals.