Mechanism of action for spreading inhibition and protection. TCR A
first binds to an agonist, which results in full downstream signaling.
At the same time, protective molecules (e.g., ERK-1) are recruited to
its neighbors (illustrated here by TCR C). Subsequently, TCR B binds to
an antagonist, which results in partial downstream signaling. This
incomplete activation results in the recruitment of inhibitory
molecules (e.g., SHP-1) to its neighbors (illustrated here by TCRs C
and D). TCR C is protected by ERK-1; thus SHP-1 fails to dock and has
no effect, whereas TCR D is inhibited. Finally, both TCRs C and D bind
to an agonist. This interaction results in full downstream signaling
for TCR C, which is protected, but there is no downstream signal
generated by TCR D, which is inhibited.