The naive (Nv), CM, EM, and effector (Eff) CD4 + T cell subsets of HD differed markedly in CCR5 expression (Nv << CM < EM ≈ Eff−; Fig. 4d, f) and differed accordingly in their susceptibility to HIV entry (Fig. 4e, g). The gene discussed is CD4; the disease is Huntington disease.