We have recently shown that ataxin-1—a polyglutamine protein implicated in the etiology of spinocerebellar ataxia type 1 (SCA1), Alzheimer’s disease (AD), and various types of cancer [3–5]—exerts a B cell-mediated protective effect on the experimental autoimmune encephalomyelitis (EAE) model [6]. The gene discussed is ATXN1; the disease is early-onset autosomal dominant Alzheimer disease.