Now, once we coat the well, we then extract the blood sample. We extract the antibodies from the blood from that individual and we take these antibodies and we place them into this well. Now, some of these antibodies will not be against the antigen and so they will not bind to that antigen. But in the case of the person who contains HIV, because they do have those antibodies against the agent, they will bind onto the antigen shown in diagram B. So these blue antibodies present in the blood of that person that contains HIV will bind onto the red antigens. Now the next question is how do we actually visualize the presence of this antibody antigen Complex well, we have to use a special antibody that we produced in the laboratory setting.