MMP9 and tropical spastic paraparesis: Based on this criterion, HTLV-1 specific CD8+ clones in HAM/TSP patients produce a wide variety of members of cyto/chemokine family, such as Interferon-gamma (IFN-γ), Tumor necrosis factor-alpha (TNF-α), Interleukin (IL)-2, Macrophage inflammatory protein 1-alpha (MIP-1α)/CCL3, beta (MIP-1β)/CCL4, and Matrix metalloproteinase-9 (MMP-9), which promote the inflammatory response (Elovaara et al., 1993).