The coordination of T-cell migration and antigen recognition is crucial for
an effective immune response. We have proposed that this coordination is a
chieved by formation of an immunological synapse between the T cell and the
antigen-presenting cell (APC). Our view contrasts with the serial encounte
r model also proposed in this issue of Trends in Immunology, which is based
on transient T cell-APC interactions when surrounded by collagen. Here, we
propose a model that reconciles immunological synapse formation and serial
encounters based on environmental control of immunological synapse formati
on.