In wild-type mice, Tat ± morphine administration markedly increases the proportion of CCL2 immunoreactive astrocytes (g) or macrophages/microglia (h) [*p < 0.05 vs. other groups in wild-type or CCL5(−/−) mice; bp < 0.05 vs. vehicle- or Tat plus morphine-treated wild-type mice; #p < 0.05 vs. equivalent treatment in wild-type mice], while in CCL5 null mice, significant increases in CCL2 immunoreactivity were only seen in macrophages/microglia co-exposed to Tat and morphine (§p < 0.05 vs. vehicle injected CCL5 knockout mice) (see, El-Hage et al.