At first glance, the nervous and immune systems appear very different. However, both systems have developed mechanisms for memory formation – though of quite different quality and significance for the organism. One striking example is that both systems form and communicate via synapses armed with similar sets of proteins. This collection of reviews, contributed by internationally recognized immunologists and molecular and cellular neurobiologists, puts side by side cellular communication devices and signaling mechanisms in the immune and nervous systems and discusses mechanisms of interaction between the two systems, the significance of which has only recently been fully appreciated.