Antigenic variation in African trypanosomes: DNA rearrangements program immune evasion.

Individual B cells express only one of the many variable-region genes of the VH gene repertoire. Likewise, individual African trypanosomes express only one surface-antigen gene of the large surface-antigen gene repertoire. In both kinds of cells, expression is controlled at the level of transcriptional activation and has been shown to involve rearrangement of genomic DNA. Here, Nina Agabian and her colleagues review recent studies on the molecular mechanisms controlling trypanosome surface-antigen gene expression.