Immunoglobulins produced by lymphoid tissue in response to a foreign substance.

• A. Antibodies
• B. Antigen
• C. Aspiration
• D. Erythema

Answer: (A)

Antibodies are the immunoglobulins produced by B cells in lymphoid tissues when the body encounters a foreign substance. These antibodies are specific proteins that bind to that foreign substance, or antigen, helping to neutralize it directly or mark it for attack by other parts of the immune system. The substance that triggers this response is called an antigen, which is why antibodies are the correct term for what’s produced. The other options don’t describe what the immune system makes in response to a foreign substance: an antigen is the trigger itself, aspiration is related to drawing in or removing material, and erythema is skin redness from inflammation.