Immune recognition of proteins: Conclusions, dilemmas and enigmas

The immune system distinguishes between two types of antigenic sites: one of these binds to immunoglobulins (IgGs) (i.e. antibodies), while the other binds to receptor molecules on T lymphocytes (i.e. the T‐cell receptors (TcRs)). The latter interaction occurs only when the antigen is presented in association with a self‐transplantation antigen, a so‐called MHC‐restriction element. This article discusses what is known about the structure of antigenic sites and their molecular interactions with antibodies, MHC‐restriction elements, and T‐lymphocyte receptors.