ICAM-1 enhances MHC-peptide activation of CD8(+) T cells without an organized immunological synapse

In addition to the TCR-ligand interaction, other receptor-ligand pairs, such as LFA-1 and ICAM-1, play a major role in the activation of T cells. Recent studies of T cell activation suggest a coordinated movement of LFA-1 and ICAM-1 in forming a defined zone in the immunological synapse. It is unclear from these studies whether the organized molecular geometry of the immunological synapse is necessary for ICAM-1 enhancement of T cell activation. In this report, we demonstrate that ICAM-1 can enhance the activation of CD8(+) T cells by MHC-peptide in the absence of an organized immunologic synapse. Therefore, although the molecular organization of the immunologic synapse may amplify stimuli, it is not an absolute requirement for either CD8(+) T cell activation or the ICAM-1 enhancement of TCR activation.