Stimulation of naïve T‐cell adhesion and immunological synapse formation by chemokine‐dependent and ‐independent mechanisms

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Abstract
Summary: Chemokines adsorbed to the cell surface play an important role in the initial interactions of T cells with endothelial cells, and may also have a role in T‐cell interactions with dendritic cells. Therefore, we examined the effect of surface‐adsorbed chemokines on the interaction of naïve murine splenic T cells with supported bilayers containing intercellular adhesion molecule (ICAM)‐1, or with bone marrow‐derived cultured dendritic cells in the presence and absence of relevant MHC–peptide complexes. Naïve T cells formed immunological synapses, defined as a ring of lymphocyte function associated (LFA)‐1–ICAM‐1 interactions surrounding a central cluster of MHC–peptide complexes, on supported planar bilayers containing ICAM‐1 and relevant MHC–peptide complexes. Chemokines stimulated an increase in the percentage of naïve cells that adhered to ICAM‐1, but did not increase the average number of LFA‐1–ICAM‐1 interactions in the contact area. In contrast, relevant MHC–peptide complexes resulted in a small increase in the proportion of interacting T cells, but stimulated an 8‐fold increase in the number of LFA‐1–ICAM‐1 interactions in each contact formed. Naïve T cells displayed a significant basal adhesion to bone marrow dendritic cells that was further increased when relevant chemokines were adsorbed to the dendritic cell surface. However, basal and antigen‐stimulated T‐cell adhesion to dendritic cells was not sensitive to pertussis toxin. Thus, there are chemokine‐independent mechanisms that initiate adhesion between T cells and dendritic cells.