Characterization of Lymphocyte Subsets in Cynomolgus Monkeys Using Flow Cytometry. Influence of Methylprednisolone

Longitudinal characterization of CD4, CD8 T-cell subsets and of haematological parameters in healthy newborns of cynomolgus monkeys

A longitudinal characterization of immune cell subpopulations (lymphocytes, CD4+ and CD8+ cells), of routine haematological parameters and of immunoglobulin serum levels was carried out in newborn Macaca fascicularis starting from 1 week up to 1 year of life. In neonates, the percentage of CD4+ lymphocytes is almost double, while the percentage of CD8+ cells is lower than that found in adult monkeys (> 5-years old). An inverted trend in the percentage of the two T-lymphocyte subpopulations was observed during the weeks following birth, with a progressive increase of circulating CD8+, paralleled by a decrease of CD4+ cell number. Consequently, the CD4/CD8 ratio slowly decreases, even if, at 12 months of life, it is still higher than that found in adult animals. Several differences were also noted between young and adult monkeys with regard to the total number of circulating CD4+ and CD8+ cells. Haematological parameters did not show consistent differences with respect to adult values. The plasma IgG level is high at birth, then decreases until 6 months of life, while the IgM and IgA values are very low during the first weeks of life but increase in the following period. Our data showed that variations of immunological (CD4+, CD8+ cells) patterns and of some haematological parameters in M. fascicularis are dependent on age. These variations should be therefore considered whenever young animals are used in experimental protocols.

Flow cytometric characterization of lymphocyte subpopulations in the cynomolgus monkey (Macaca fascicularis)

Characterization of immune cell subpopulations in the cynomolgus monkey was performed using a direct immunofluorescence technique adaptable for routine and repeated monitoring. This whole blood procedure is faster and requires less volume than conventional density gradient isolation methods. Low intra- and inter-animal variations were seen in hematology parameters and in CD4, CD8, and CD20 lymphocyte subtypes. CD4 values were 28% of lymphocytes in males and 30% in females. Fifty-six percent were CD8+ in males and 54% in females. CD4:CD8 ratios were approximately 0.5 in both sexes. This proportion is the reverse of that observed in humans, but appears normal for the cynomolgus. Consistent with values reported for humans, approximately 12% of cynomolgus peripheral blood lymphocytes were CD20+. Greater than 95% of the lymphocytes present in blood were identified as CD4, CD8, or CD20 positive.