CCL2 and asthma: Indeed, a study reported that the MCP-1 -2518 A>G polymorphism has strong linkage disequilibrium with other MCP gene polymorphisms, and the combination of MCP-1 -2518 A>G, MCP-2 +46A>C, and MCP-3 +563C>T was the best predictive model for asthma (19).