Interaction of T-cell antigen receptors with antigen/major histocompatibility complex (MHC) molecule complexes on antigen-presenting cells (APC) leads to T-cell activation. Additional interaction between adhesion molecules on the APC and their ligands on T cells is required for optimal T-cell activation. In vitro cultured human epidermal Langerhans cells (cLC) are powerful APC that express adhesion molecules LFA-3 and ICAM-1. Both molecules on cLC serve a functional role in the generation of a T-cell response.