Potassium dichromate is an important metal antigen in the occupational environment, which seems to affect morphology and function of macrophages and therefore induce a decreased resistance to a variety of infectious agents. Trying to understand if the metal exerts in differents dosages (3, 30, 300 µg/ml) an effect on the coli-activated neutrophyles, their functional responses were investigated "in vivo": (1) at 15' and 30' after incubation of dichromate with peripheral blood and subsequent addition of bacteria. (2) after exposure of peripheral blood with the metal in presence of bacteria.

All treated samples were incubated at 37° during 15' with the FITC-labeled E. coli suspension, washed, the red blood cells lysed, total DNA stained and subquently analysed by flow cytometry.

The results of flow cytometry assay were comparable to those obtained with a conventional microscopic method. It was found that potassium dichromate suppressed in a dose-response and incubation-time relationship the activity of coli- activated neutrophyles by 10% to 50% when comparing to the control value. It can be concluded that the flow cytometric analysis is an adquated method to study the celular effects of antigens "in vivo".