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.