Zwitterionic capsular polysaccharides: The new MHCII-dependent antigens

Abstract

The immune system has evolved the ability for T cells to recognize nearly any biological polymer, including peptides, protein superantigens, and glycolipids through presentation by the major histocompatibility complex (MHC) proteins such as MHC class I (MHCI), MHC class II (MHCII), and CD1. A recent and unexpected addition to this list is the zwitterionic capsular polysaccharide (ZPS). These bacterial molecules utilize MHCII presentation to activate T cells via recognition by αβ T cell receptor (αβTCR) proteins. In this review, we explore what is currently known about ZPS processing and presentation within antigen-presenting cells (APCs) and the immune response that follows. © 2005 Blackwell Publishing Ltd.