title: Conditions for pathogen elimination by immune systems.
abstract: A continuous harvest effort can lead a population to extinction. How an "unconscious" immune system would perpetrate such an effort in order to eliminate a self-replicating antigen (a pathogen) becomes an intriguing problem if the system responses are functions of the pathogen population: the responses cannot be a continuous effort as the pathogen vanishes. On theoretical grounds, we show some qualities an immune response must have to support pathogen elimination. Then, three specific mechanisms are addressed: a pathogen-independent positive feedback loop among the responding cells of the system (e.g., B-lymphocyte and T-helper); the persistence of antigen bound to presenting cells; and the programmed expansion/contraction of a pool of responding cells. The maintenance of responding cells due to these mechanisms is the essential feature to the effective clearance of self-replicating agents. Thus, evolutionarily, the primary function of a helper lymphocyte would be to amplify a response and the primary function of memory would be the very elimination of pathogens.
authors.affiliation: Departamento de Fisiologia, Instituto de Biociências, da Universidade de São Paulo, Rua do Matao tr. 14, 321, 05508-900, São Paulo, SP, Brazil, jgcb@usp.br.
authors.forename: José Guilherme
authors.initials: JG
authors.lastname: Chaui-Berlinck
authors.forename: José Alexandre Marzagão
authors.initials: JA
authors.lastname: Barbuto
authors.forename: Luiz Henrique Alves
authors.initials: LH
authors.lastname: Monteiro