Mechanisms of dendritic cell-induced T cell proliferation in the primary MLR assay

DC are unique antigen presenting cells, and their ability to induce prolife ration of T cells in a mixed leukocyte reaction (MLR) assay is commonly use d for the evaluation of their function. To determine the mechanisms involve d in DC-induced T cell activation in a primary MLR assay, a variety of diff erent agents were examined in this study that interfere with DNA synthesis, membrane organization, protein synthesis, and maturation induced by bacter ial products. While only live DC were able to induce T cell proliferation i n the MLR assay, irradiation of DC did not influence their stimulatory capa city. Fixation of DC membrane with paraformaldehyde resulted in a loss of D C capacity to induce T cell proliferation demonstrating that physical organ ization of the plasma membranes plays an important role in the induction of T cell activation. In addition, the pretreatment of DC with cycloheximide revealed that protein synthesis was not critical for the ability of DC to a ctivate T cells. Finally, Staphylococcus aureus-mediated activation of DC s ignificantly increased T cell proliferation and this effect was not depende nt on IL-12 production of DC since DC generated from IL-12 knockout mice we re not different from wild type DC. In summary, these data suggest that DC membrane structures are responsible for the antigen presentation and co-sti mulation and play a key role in T cell recognition and activation by DC. (C ) 2001 Elsevier Science B.V. All rights reserved.