Figure 1. Paracrine signaling between the SR and DF, as well as within the DF only, ultimately results in the synthesis and secretion of the chemotactic molecules MCP-1 and CSF-1 for the recruitment of mononuclear cells into the DF. Note that a given molecule can often enhance the expression of more than one gene, and that two chemokines (MCP-1 and CSF-1) with redundant functions are produced. "Enhances" refers to up-regulation of a given gene, and "recruitment" is the chemotactic effect of CSF-1 and MCP-1. Modified from Wise (1998a).