Monoclonal antibody MNA.1 (formerly known as 5D3-F7) recognizes human natural and recombinant monocyte chemotactic protein-1 (MCP-1). Monocyte chemotactic protein-1 (MCP-1) is a 11 kDa protein belonging to the CC subgroup of the chemokine superfamily, which stimulate the migration of monocytic cells. In contrast, the CXC chemokines predominantly activate polymorphonuclear leukocytes. The coordinated synthesis and release of MCP-1 plays a central role in both acute and chronic inflammatory processes by controlling the influx of phagocytic cells. Furthermore, their state of activation is in concert with primary inflammatory cytokines, such as IL-1, TNF-a, and IL-6. A selective accumulation of MCP-1 in the cerebrospinal fluid (CSF) of AIDS patients with cytomegalovirus encephalitis, but not with other opportunistic infections or primary lymphomas of the central nervous system , has been described. Furthermore, the chemotactic activity of MCP-1 on monocytic cells has been suggested to play a role in psoriasis, rheumatoid arthritis and atherosclerosis. No cross-reactivity of mAb MNA.1 with other cytokines has been detected.