Figure 6. MCP-1 expression in HAEC, monocytes, and HAEC/monocyte co-cultures. P. gingivalis 381 (wt) or the fimA mutant DPG3 (fimA) was used to infect HAEC (A) human monocytes or (B) HAEC/human monocyte co-cultures (C) at an MOI of 1:100 (100) or 1:500 (500), and MCP-1 was measured by ELISA after 24 hrs. Uninfected HAEC, monocytes, and HAEC/monocyte co-cultures (control) served as negative controls. Analysis of these data demonstrates that cultures of primary HAEC, human peripheral blood monocytes, and HAEC/monocyte co-cultures actively respond to P. gingivalis challenge. Moreover, the MCP-1 response observed in the co-culture system is not simply additive, but rather, some unknown interaction occurs between endothelial cells and macrophages during P. gingivalis challenge, giving rise to a synergistic response.