Immune System Practice Test

Which organ produces most plasma proteins?

Liver Spleen Kidneys Lymph nodes

Correct Answer:

Liver

Explanation:

The body relies on the liver to make the majority of circulating plasma proteins. Hepatocytes synthesize albumin, which is the most abundant plasma protein and helps maintain the blood’s oncotic pressure, keeping fluid in the vessels. The liver also produces many clotting factors—such as fibrinogen and prothrombin—and a range of other plasma proteins like transferrin and ceruloplasmin that carry substances or have regulatory roles. While some proteins (like immunoglobulins) come from immune cells elsewhere in the body, the liver remains the main source of most plasma proteins. Other organs listed mainly handle immune function, filtration, or hormone production and do not serve as the primary producers of plasma proteins. That’s why the liver is the best answer.

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