As we have previously observed [38], peripheral blood CD4+ T cells from HD expressed high levels of CD28 (mean = 92) but very low levels of HLA-DR (mean = 3.4), B7.1/CD80 (mean = 1) and B7.2/CD86 (mean = 6.8) molecules (Figure 2a,b). This evidence concerns the gene CD28 and Huntington disease.