Glycosidase trimming inhibitors may be used to study contribution of N-linked glycan moieties in T cell function. We have studied the effects of castanospermine (Cas), swainsonine (Swain), 1-deoxynojirimycin (dNM), and 1-deoxymannojirimycin (dMM) on T cell activation and differentiation. Our analysis included a new dNM derivative, N-pentyl-1-deoxynojirimycin (pentyldNM). Previous reports showed inhibitory action of trimming inhibitors, such as Swain and Cas, on pokeweed mitogen-driven immunoglobulin (Ig) production. We extend these findings for pentyldNM and observed that glucosidase inhibitors, Cas and pentyldNM were effective in inhibiting CD2 and CD3 monoclonal antibody (mAb) driven Ig production. The pattern of inhibition by mannosidase and glucosidase inhibitors correlated with inhibitory action on T cell activation: only glucosidase trimming inhibitors (Cas and pentyldNM with comparable potency) perturbed mAb-induced T cell activation, in particular if induced by CD2 mAb. Expression of the early activation marker CD69 was not decreased in the presence of these inhibitors, while addition of exogenous recombinant interleukin-2 partially overcame inhibitory effects during proliferation. These findings suggest that glucosidase, but not mannosidase, trimming inhibitors interfere with a late phase of T cell activation. In addition, the enhanced sensitivity of CD2 mAb-induced proliferation for glucosidase trimming inhibitors suggests dependence on N-linked glycans during CD2-mediated adhesion and triggering functions.