LAUSR

Background Since the time when Paul Ehrlich conceived the term “horror autotoxicus”, autoantibodies have been associated with the development of autoimmune diseases. However, several works have recently shown the presence of autoantibodies in sera from healthy subjects (n=489), who do not develop autoimmune diseases. Objectives Here, we report a network of immunoglobulin G (IgG) autoantibodies targeting G protein-coupled receptors (GPCRs), growth factors and growth factor-related molecules in sera from healthy subjects. Methods Autoantibody levels in sera were assessed using ELISA. Autoantibody network was analysed by exploratory factor analysis (EFA), dandelion plot method, hierarchical clustering, and multi-study factor analysis (MFA). We also reverse engineered autoantibody functions through in silico evaluation of autoantibody target interactions using STRING and gene ontology (GO). To test the autoantibodies functionality we assessed the in vitro production of IL-8 by PBMCs and neutrophil migration in response to IgG from healthy subjects as well as ETAR-immunised and control mice. Leukocyte cellularity to secondary immune organs was analysed comparing ETAR-immunised with control mice. Results Gender, age and the presence of pathological conditions (systemic sclerosis n=84, Alzheimer’s disease n=91 and ovarian cancer n=207) changed correlations between the autoantibodies and their hierarchical clustering distribution. Notably, subjects at age below and above 65 years or with pathological conditions exhibited particular autoantibody hierarchical clustering signatures. In addition, females at age above 65 years, representing the group of subjects with higher risk to develop SSc, displayed the closest link to SSc in terms of autoantibody hierarchical clustering. Finally, autoantibody directed against the endothelin receptor type A (ETAR) showed an essential role in the autoantibody network by orchestrating neutrophil trafficking in vitro and in ETAR-immunised mice. Conclusions Our data provide a framework for the existence of a physiological network of autoantibodies and reveal a new paradigmatic view on these physiological molecules. Disclosure of Interest None declared