Discrimination of B, T and null lymphocytes by esterase cytochemistry

A technique has been devised which optimally demonstrates non-specific esterase activity in human blood lymphocytes. The reaction is carried out on smears fixed with formalin vapour, using alpha-naphthol butyrate as substrate at pH 8 and at a low concentration for a short incubation period. The pattern of esterase activity revealed by this method provides a discriminating marker for mature T-lymphocytes, which show dense, localised, dot-like positivity, and a probable marker for 'null' cells in the form of scattered granular positivity. B cells appear to be negative. Monocytes show a clearly different pattern of granular positivity.