of contaminant DC.Maximal responsiveness of monocytes to calcium ionophore observed under the following conditions:high cell density (3.times.10.sup.6 monocytes per well on standard 24 well plate or higher density)small monocyte size (smaller monocytes display greater upregulation of B7.1 and downregulation of CD14, for example, than larger monocytes; however, including adjunct cytokines such as r