Huntington disease (HD) is an incurable neurodegenerative disease caused by a mutation in the huntingtin gene (htt). Though most of the symptoms of HD are neurological, the mutant HTT protein is expressed in non-neural cells as well. In this issue of the Journal of Clinical Investigation, researchers led by Paul Muchowski at the J. David Gladstone Institutes in San Franscisco examined the role of immune cells in HD. Immune cells known as microglia, which were isolated from the brains of HD mice, as well as immune cells from the peripheral blood were found to be defective in their ability to migrate. Interestingly, the immune cell defects were apparent prior to the onset of HD symptoms. This study suggests that changes in immune cell function may underlie some of the symptoms of HD.