Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

A beta-sheet sandwich structure is common to all types of these whose Fab and Fc regions can be separated by papain based on their crystallizability. Their effector functions are increased through CSR, while somatic hypermutation occurs in their variable regions and renders a higher affinity for binding sites. They are used in the ELISA process, and Kohler and Milstein got the Nobel in Medicine for producing the monoclonal varieties of these. They can easily change isotypes, of which humans have five, and they attach to epitope of their targets by induced fit. For 10 points, name these y- shaped proteins produced by B Cells, that target and attack foreign antigens.
Science