Macrophage defects with advanced a ge. Arrows (↑, ↓ or ↔) denote increased, decreased or unaltered levels in the aged compared to the young. Abbreviations: IFN-γ, interferon-gamma; ROS, reactive oxygen species; MHC, major histocompatibility complex; RNS, reactive nitrogen species; iNOS, inducible nitric oxide synthase; LBP, LPS-binding protein; JNK, janus kinase; MAPK, mitogen activated protein kinase; PGE2, prostaglandin E2; I-κB, inhibitor of κB; NF-κB, nuclear factor-kappaB; COX, cyclooxygenase; TNF-α, tumor necrosis factor-alpha; MIP, macrophage inflammatory protein; IL, interleukin.