Neuraminidase-treatment greatly increased 3H-thymidine incorporation by human lymphocytes at lower concentrations of Con A. An irreversible sequence after 24 hr of incubation in the presence of the optimal concentration of Con A was found. However, at a suboptimal concantraiton of Con A, neuraminidase-treated lymphocytes exposed to Con A for 72 hr exhibited a greater magnitude of 3H-thymidine incorporation in contrast to the neuraminidase-treated lymphocytes exposed to Con A for 24 hr, indicating that the enancement effect of neuraminidase was not due to the increased binding of Con A to cell surfaces.This work was supported in part by Grant-in-Aid for Scientific Research (Project Nos. 544050 and 577401) from the Ministry of Education, Science and Culture of Japan
