Immune response to parasitic attack: evolution of a pulsed character.

Pulsed characters are temporary biochemical, cellular, or structural changes produced in response to environmental or biotic challenge. For example, response to parasitic attack develops as a pulse of defensive chemicals or cells that typically decay after the parasite has been controlled. Almost all theories for the genetic variability of characters assume measurements on static characters. This paper presents theoretical tools to examine optimal control variables for pulsed characters and the expected level of genetic variability in those control variables. The example of host immune response to parasitic attack is used to develop the theory.