Major histocompatibility complex class II antigen presentation in Hodgkin's disease

The malignant cells in Hodgkin's disease (HD), commonly referred to as Hodgkin and Reed-Sternberg (HRS) cells, express major histocompatibility complex (MHC) class II molecules and, like "professional" antigen-presenting cells (APCs), different accessory or costimulatory molecules which can provide an additional activation signal to T cells. Despite expressing the key effector molecules of APCs, HRS cells fail to evoke an effective T cell response in vivo. Previous work addressing this paradox has shown that in a large proportion of HRS cells MHC class II molecules present the non-immunogenic MHC class II-associated invariant chain peptide (CLIP). The inability of many HRS cells to present MHC class II-associated antigenic peptides to surrounding helper T lymphocytes could explain how these malignant APCs can thrive in a hostile environment of apparently immunocompetent cells.