While IgG1 is the most predominant IgG subclass in healthy adults (more than 60% of total IgG) and IgG4 by far the rarest (approximately 5% of total IgG) (58–61), IgG4 is of special interest not only because it is related to autoimmunity but also because of its anti-inflammatory properties and its coexistence with Th2-driven IgE (allergic) responses (62). This evidence concerns the gene IGHE and Autoimmunity.