Dictionary #4

Dark Zone: A portion of the germinal center that is the site of rapid cell division by forms of B cells called centroblasts.

Superantigens: Any substance that binds to the V-beta domain of the T-cell receptor and residues in the chain of class II MHC molecules. It induces activation of all T cells that express T-cell receptors with a particular V-beta domain. It functions as a potent T-cell mitogen and may cause food poisoning and other disorders. 

Tapasin: TAP-associated protein. Found in the ER that brings the TAP transporter into proximity with the class I MHC molecule, allowing it to associate with antigenic peptide.