Antigens are cellular parts that are able to bind to antibodies. Antigens are usually made out of proteins or polysaccharides, so they include parts like the coats, capsules, or cell walls of pathogens (disease-causing bacteria, viruses, and other microorganisms). Antibodies are proteins that are produced by the immune system to prevent the growth and spread of pathogens. Antibodies bind to antigens, like keys fitting into specific locks.

Which of the following diagrams best represents an antigen-antibody complex?

W.
X.
Y.
Z.
A.
Z
B.
Y
C.
W
D.
X