Where would you expect to find antibodies in the human body? (A) In the blood, in the lymph nodes, and attached to the membrane of B lymphocytes. (B) In the bone marrow, in the spinal cord, and attached to the membrane of T lymphocytes. (C) Attached to the membranes of B and T lymphocytes. Or (D) in the lymph nodes only.
Antibodies are produced by B cells or B lymphocytes, which are a type of white blood cell that functions in the adaptive immune system. Antibodies exist in two forms: either they exist on the surface of the B cell as a B cell receptor or they’re secreted as a soluble antibody.
Antibodies are specialized proteins that combine to antigens or foreign substances like those that are found on the surface of a pathogen. So when there’s an infection, the antibody on the surface of the B cell can bind to the antigen on the pathogen. This initiates different responses from the B cell, including the production of specialized B cells that secrete antibodies against this pathogen. These antibodies can then circulate through the blood and lymph where they might encounter other pathogens with the same antigen. This way the whole body can be surveyed for pathogens which can then be eliminated by the antibody itself or by other cells of the immune system.
Therefore, you would expect to find antibodies in the blood, in the lymph nodes, and attached to the membrane of B lymphocytes.