Alpha-naphthyl acetate esterase activity is not a specific marker for ovine T lymphocytes

Alpha-naphthyl acetate esterase (ANAE) activity was demonstrated in ovine lymphocytes harvested from blood on Ficoll-metrizoate gradients. The enzyme's specificity for T lymphocytes, identified by immunofluorescent staining of T cell-specific antigens, was assessed. Correlation analysis of the results obtained using unfractionated lymphocytes from 12 sheep showed no correlation between ANAE activity and the expression of T cell antigens (r = 0.22). When lymphocytes from 4 sheep were fractionated on nylon wool columns a mean of only 43.2% of the cells in the non-adherent population were ANAE-positive whereas 94.7% of these cells were identified as T lymphocytes. Blood lymphocytes from 5 animals were separated into 3 fractions using Percoll discontinuous density gradients. No significant relationship was seen between ANAE activity and T cells in Fractions 1 and 3 (r = 0.41 and 0.21). Fraction 2 cells, however, did show a significant positive relationship (r = 0.91) between these two features but the biological significance of this relationship is unknown. It was concluded that ANAE activity is not a specific marker for ovine T lymphocytes.