Costimulation and the regulation of antimicrobial immunity.

The regulated expression of costimulatory molecules is a major factor limiting T-cell responses to self-antigens. However, the development of effective antimicrobial immunity requires that these molecules be induced on a variety of tissues, but most notably on macrophages. Here, Paul Kaye discusses the regulation of costimulatory molecules on macrophages and suggests that microbial interference in this process has important implications for immune regulation.