To determine whether binding of human rhinovirus (HRV) to intracellular adhesion molecule-I might disrupt airway immune processes, effects of a major HRV group, HRV-16, on T cell proliferation and cytotoxicity were defined. HRV (1-10 TCID₅₀/cell)significantly inhibited T cell proliferation induced by antigen but not proliferation secondary to mitogens, interleukin-2, or an irradiated allogeneic T cell line. Noninfectious (UV-irradiated) HRV had similar effects. Inhibition of T cell proliferation was dependent on HRV binding to intercellular adhesion molecule-l on monocytes, indicating that the virus interferes with lymphocyte activation indirectly through effects on antigenpresenting cells. In addition, HRV inhibited T cell cytotoxic responses but not NK cell activity. if these effects also occur in vivo, the resulting disturbance in local airway immunity could increase the chances of successful viral replication, and might also be a factor in the pathogenesis of secondary viral or bacterial respiratory tract infections.