Plasma membranes of many cell types contain domains enriched in specific li
pids and cholesterol, called lipid rafts. In T lymphocytes, key T cell anti
gen receptor (TCR) signalling molecules associate with rafts, and disruptin
g raft-association of certain of these abrogates TCR signalling. The TCR it
self associates with lipid rafts, and TCR crosslinking causes aggregation o
f raft-associated proteins. Furthermore, raft aggregation promotes tyrosine
phosphorylation and recruitment of signalling proteins, but excludes the t
yrosine phosphatase CD45. Together the data suggest that lipid rafts are im
portant in controlling appropriate protein interactions in resting and acti
vated T cells, and that aggregation of rafts following receptor ligation ma
y be a general mechanism for promoting immune cell signalling.