Identification of cynomolgus T lymphocytes by acid alpha-naphthyl acetate esterase staining and spontaneous erythrocyte rosette formation

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.

Phenotypic characterization of cynomolgus monkey natural killer cells

Natural killer (NK) activity of cynomolgus monkey peripheral blood lymphocytes (PBL) was determined using B95-8 cells as target cells. Examination for the reactivity of human NK-related monoclonal antibodies (mAbs), anti-Leu-7, anti-Leu-11b, anti-NKH1A, and NC-1, with cynomolgus PBL revealed that Leu-11b (CD16) was the only antigen expressed on cynomolgus PBL. The percentage of Leu-11b-positive (Leu-11b+) cells correlated well with the level of NK activity when PBL taken from 21 monkeys were tested. After depletion of Fc receptor-positive (FcR+) cells, NK activity was lost concomitantly with the disappearance of Leu-11b+ cells. These results show that cynomolgus NK cells are mainly FcR+ which can be detected by mAb directed to Leu-11b. Cynomolgus PBL were separated by Ficoll-Hypaque centrifugation after E rosette formation with 2-aminoethylisothiouronium bromide-treated sheep red blood cells, and NK activities of both E rosette-forming (E+) and nonforming (E-) fractions were determined. The high level of killing was observed in the E- fraction, suggesting that the majority of cynomolgus NK cells was contained in the E- fraction. The separation of PBL by Percoll discontinuous density gradient showed cynomolgus NK cells were enriched in the low density fractions.

Suppressor macrophages in lymphocyte proliferation of cynomolgus monkeys

The present study demonstrated the presence of cells belonging to monocyte/macrophage lineage which suppressed mitogen-induced blastogenesis of peripheral blood lymphocytes in cynomolgus monkeys. Depletion of adherent or phagocytic cells from peripheral mononuclear cells caused a substantial increase in the blastogenic response of cynomolgus monkey lymphocytes whereas the same treatment led to marked reduction rather than enhancement in human lymphocyte blastogenesis. Addition of thioglycollate-elicited peritoneal exudate adherent cells as macrophages suppressed the blastogenic response of nonadherent lymphocytes in a dose-dependent manner. The suppressive effect was observed not only in autologous but also in allogeneic macrophages to the responder lymphocytes. Treatment of macrophages with silica, carrageenan or freezing-thawing reduced their suppressive effect but there was no reduction with mitomycin C or indomethacin. No suppressive activity was detected in the cell-free supernatant of macrophages cultured in the presence or absence of mitogens for up to 4 days. From these findings, it appeared that monocyte/macrophage lineage might be responsible for the observed suppressive effect on mitogen-induced blastogenesis of cynomolgus monkey lymphocytes.