IL6 and infection: BAL fluid levels of IFN-α, IFN-γ, TNF-α, IL-6, MCP-1 and MIP-2 increased following infection, with levels of IFN-γ and MCP-1 being significantly higher in Ctsl-/- mice than in Ctsl+/+ mice (at days 7 and 14, respectively; Fig 7).