I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "The humoral (antibody) response is defined as the interaction between antibodies and antigens. Antibodies are specific proteins released from a certain class of immune cells known as B lymphocytes, while antigens are defined as anything that elicits the generation of antibodies ("anti"body "gen"erators). Immunology rests on an understanding of the properties of these two biological entities and the cellular response to both."? 

What are antibodies continually communicating with?