TNF and retinal degeneration: Several cytokines and chemokines including MIP-1α (CCL3), MIP-1β (CCL4), MCP-1 (CCL2), MCP-3 (CCL7), TNF-α, IL-1β and IL-6 have been implicated in photoreceptor-microglial crosstalk and retinal degeneration [18, 31, 41–45].