The importance of mosaic genes to trypanosome survival.

African trypanosomes possess several elegant ways to evade the immune defenses o f mammalian hosts. They have an extensive repertoire o f genes for a variant surface antigen and recent data show that this finite repertoire can be further amplified by mosaic gene formation and point mutation, producing an almost limitless capacity to vary. The significance of these mechanisms of antigenic diversity to trypanosome biology and the parasite-host relationship in general are discussed here by Anthony Barbet and Sondra Kamper.