Uptake into macrophages

Dear all -

We are using differentiated THP-1 cells as a macrophage-like cell to look at receptor
mediated uptake of immunoglobulin.  We are FITC labeling the immunoglobulin and looking
both under the microscope and with the flow.  Is there a optimal time frame at which to
look (1 hr, 6hr, overnight)??  Is there a good method to differentiate between
internalization vs. external surface binding? Any appropriate references?

Thanks!

Dan Smith
San Diego