Signaling and communication are important at different levels of biolo
gical organization. Signals exchanged between cells of the immune syst
em initiate and coordinate the immune response; signals exchanged betw
een individuals often coordinate social behavior. Behavioral ecologist
s interested in the evolution and functional design of signals exchang
ed between individuals have produced a theory of signaling and communi
cation that stresses the importance of cooperation and conflict; if a
conflict of interest between signaler and receiver is great enough, si
gnals evolve towards greater reliability. We suggest that the applicat
ion of signaling system theory to signals exchanged between cells with
in an individual will allow for a better understanding of immunity and
intra-individual communication in general, with potential for novel a
pproaches to the treatment of disease.