The logic of intercellular communication in the immune system.

The collaboration between T and B lymphocytes is used as an example to illustrate how the key features of immune regulation (cell interaction, reciprocal exchange of signals by cell contact, and dependence on soluble cytokines) serve as amplifying reactions. By linking cell-based amplifiers in sequence, the resulting immune response is made highly sensitive to small changes in the environment. Thus, intercellular communication in the immune system can be viewed as a higher level analogue to the kinase cascades that amplify intracellular signalling mechanisms.