Questions: Humoral defense of the body is an immune system function mediated by: lymphocytes. antibodies. mucous. antigens.

The answer is the second one: antibodies.

Explanation for each option:

1. Lymphocytes: These are a type of white blood cell that play a crucial role in the immune system, particularly in the adaptive immune response. However, they are not directly responsible for humoral defense. Instead, B lymphocytes (a subtype of lymphocytes) produce antibodies, which are the actual mediators of humoral immunity.

2. Antibodies: These are proteins produced by B cells (a type of lymphocyte) that specifically recognize and bind to antigens. Antibodies are the primary mediators of humoral immunity, as they circulate in body fluids and help neutralize pathogens.

3. Mucous: This is a protective secretion produced by mucous membranes. While it plays a role in trapping pathogens and preventing their entry into the body, it is not a mediator of humoral immunity.

4. Antigens: These are substances that can provoke an immune response, often by being recognized as foreign by the immune system. They are not mediators of humoral defense but rather the targets that antibodies bind to.

In summary, humoral defense is primarily mediated by antibodies, which are produced by B cells and function to neutralize and eliminate pathogens in body fluids.