The function of antibodies

Summary Antibodies have multiple biological activities. They can both recognize and act on specific antigens. They can protect against and cause serious diseases, enhance and inhibit antibody responses, enable survival, and threaten life. Which among their many, often antagonistic properties explains that antibodies were selected half a billion years ago and transmitted to mammals across millions of generations? In other words, what is the function of antibodies? Here I examine how their structure endows antibodies with unique cognitive and effector properties that contribute to their multiple biological activities. I show that rather than specific properties, antibodies have large functional repertoires. They have a cognitive repertoire and an effector repertoire that are selected from larger available repertoires, themselves drawn at random from even larger virtual repertoires. These virtual repertoires provide the adaptive immune system with immense, constantly renewed, reservoirs of cognitive and effector functions that can be actualized at any time according to the context. I propose that such a flexibility, which enables living individuals to adapt to a rapidly changing environment, and even deal with an unknown future, may provide a better selective advantage than any particular function.