Immunocompromised host: From the early events until the impact of acquiredimmunodeficiency syndrome

The concept that microorganisms can modulate the host resistance was histor ically reviewed in the present article. The importance of African trypanoso miasis in the development of the research on immunosuppression as well as t he impact of human immunodeficiency virus infection are discussed. Each day new opportunistic organisms establish a constant challenge for the correct diagnosis of concomitant infections in acquired immunodeficiency syndrome. The importance of parasite infection bz the balance of host resistance in the third world was emphasized. Finally, some aspects of Leishmania as oppo rtunistic organisms were presented.