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.

In flow cytometry, these molecules bind to fluorophores to differentiate test cells, and HRP is bound to them for use in another process. Kohler and Milstein discovered that myeloma cells can produce the monoclonal variety of these molecules. Three layers of these are used in the "sandwich" variety of the ELISA technique, and these proteins exhibit disulfide bonds between their two heavy and light chains to form a Y-shaped structure. The type of these molecules which attack A and B blood groups is known as Immunoglobulin M. Released by plasma B cells, for 10 points, name these proteins produced by the immune system which each tag a unique antigen.
Science