IGHG3 and Ataxia: Further indirect findings in favour of a pathogenic role of anti-Tr include the strong association of anti-Tr with ataxia in patients with HD, with the antibody being virtually absent in patients with HD and no PCD, the intrathecal synthesis of anti-Tr, the observation that DNER knockout causes ataxia in mice, and from the predominance of complement-activating IgG1 and IgG3 antibodies among anti-Tr subclasses (which may suggest a Th1-type response of CD4+ T helper cells).