Humoral immunity is a type of immunity which is conferred through the release of antibodies which are used to target cells for destruction by the body when these cells are viewed as potentially dangerous. This type of immunity is a complement to cellular immunity, in which cells release toxins to kill unwanted invaders, or attack the invaders directly to kill them. Together, humoral and cellular immunity are designed to defend the body against a wide variety of threats which could compromise it.

The term “humoral immunity” is a reference to the fact that this type of immunity is mediated by cells which float in the blood and lymph, or “humors” of the body. When researchers first began to explore the concept of humoral immunity in the 1800s, many of them believed in medical theories dating back to ancient times which included the idea that the balance of the body was maintained with “humors,” substances which flowed through the body and caused various effects. While the humors theory has since been debunked, it lingers on in medical terminology and in many languages; describing someone is “choleric,” for example, is a reference to one of the supposed humors.

This form of immunity originates in the B-cells, specialized cells which come from the bone marrow. B-cells are designed to produce antibodies when stimulated to do so, most commonly by T-cells which recognize antigens and trigger the production of antibodies by the B-cells. The B-cells essentially turn into little antibody factories in the blood, floating around to mop up as many of the invaders as possible.

People can acquire humoral immunity by being exposed to viruses, bacteria, and other substances which can cause harm, and they are also usually born with some innate immune responses which are designed to recognize broad types of cells and organisms which could cause a threat to the body. Acquired immunity is important because it allows a body to adapt to its environment by developing new antibodies as needed.

When people develop problems with their humoral immunity, they are more susceptible to developing infection and disease. Conditions like HIV attack the immune system directly to make it less functional, and humoral immunity can also be compromised with the use of certain medications, such as chemotherapy and the drugs used to prepare people for organ transplant. In individuals who have been compromised, aggressive and prompt treatment is critical for infections to prevent the body from being overwhelmed by something which it cannot fight.