Characterization of lymphocyte subpopulations in the blood of the cynomolgus monkey using flow cytometry

This study was performed to assess the usefulness of flow cytometry in comparison with acid alpha-naphthyl acetate esterase (ANAE) staining for the enumeration of lymphocyte subpopulations in cynomolgus monkeys. For flow cytometry, use was made of mouse antihuman leukocyte monoclonal antibody (T11), recognized to undergo cross-reaction with monkey T lymphocytes or antimonkey IgG serum labelled with fluoroscein isothiocyanate. The percentages of lymphocyte subpopulations in mononuclear cells of thirty healthy female cynomolgus monkeys were 72.1 +/- 2.4% for T cells and 24.6 +/- 2.4% for B cells as assayed by flow cytometry evaluation, and 63.8 +/- 2.5% for T cells and 15.8 +/- 2.2% for B cells as determined by ANAE staining. Although the percentage of T cells shown by ANAE staining was significantly lower than that seen with flow cytometry, the coefficient of correlation indicated a close correlation in both T and B cell subsets between these two methods. In monkeys receiving 20 mg kg-1 cyclophosphamide daily for 14 days, counts of all leukocytes and T and B cells were decreased, whereas animals treated with 1.0 mg kg-1 muroctasin daily for 14 days showed higher monocyte and neutrophil counts without changes in T or B cells. These results suggest that flow cytometry evaluation has several advantages over ANAE staining with respect to rapidity and precision in toxicological studies using large numbers of monkeys.