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Humoral immunity produces antibodies that mark foreign material in the bloodstream for destruction. B cells recognize antigens and multiply to release antibodies that attach to invading organisms. The immune system accumulates memories of previous attacks, providing long-term immunity. Vaccinations stimulate humoral immunity and create immune memory. Immune system problems, such as autoimmune diseases, can impair humoral immunity. The term “humoral immunity” comes from the cells that float in the blood and lymph of the body.
Humoral immunity is a means by which the body protects itself from infection by producing antibodies that target foreign material in the bloodstream that is seen as potentially dangerous, marking it for destruction. It is part of the adaptive immune system, which activates in response to a specific threat, as opposed to the innate immune system, which is continuously active but less effective. The other part of the adaptive system is cellular, or cell-mediated, immunity, in which cells release toxins to kill invaders or attack them directly, without the involvement of antibodies. Together, humoral and cellular immunity are designed to defend the body against a wide variety of threats that could compromise it.
How does it work
This form of immunity begins in specialized white blood cells known as B cells, which are produced by the bone marrow. They recognize antigens, which are certain molecules, such as some proteins, on the surface of a virus or bacterium. There are several types of B cells, each designed to respond to a particular antigen. When one is encountered, the B cell multiplies, producing huge numbers of individuals that release antibodies designed to attach to the antigen on the invading organism; they essentially turn into little antibody factories in the blood, floating around to target as many invaders as possible. Once marked by these antibodies, the invaders will be destroyed by other immune cells.
When the invader is removed, many of the B cells produced to counter this specific threat will die, but some will remain, depositing themselves in the bone marrow and serving as a kind of ‘memory’ of this attack. People are born with a set of innate immune responses designed to recognize broad cell types and organisms that could pose a threat to the body, but humoral immunity is acquired from exposure to viruses, bacteria, and other substances that can cause harm. Over time, the body accumulates more “memories” of previous onslaughts by harmful microorganisms.
long-term immunity
The humoral immune response can produce long-lasting immunity to many infectious agents. When the body is attacked by an agent, such as a virus, that it has never encountered before, it has to start over and typically takes several days to mount an effective immune response. During this time, the virus can multiply unchecked, causing an infection that can produce unpleasant and possibly dangerous symptoms. It is only when the body has produced a large number of suitable antibodies that it can fight the infection. If, however, it encounters this virus again, it will usually be much better prepared, thanks to the retention of B cells produced in response to the previous attack, and will be able to get to work eliminating the invader immediately.
Vaccination
This immune “memory” is also how immunizations and immunizations work. People can be injected with dead or inactivated forms of a dangerous virus or bacteria that will stimulate a humoral immune response without posing a threat to the body. If, in the future, this person is exposed to the real agent, there should be an immediate immune response that will clear it out before it can cause serious harm.
Vaccination is more effective for some types of infections than for others. A worldwide vaccination program for the smallpox virus succeeded in bringing about its complete extinction in the wild, as no human host could be found that was not immune. Unfortunately, some viruses mutate rapidly, causing changes to compounds on their surfaces that the humoral immune system uses to recognize them. This is why new flu vaccines must continually be developed. People vaccinated against this rapidly mutating virus may not be immune to a new strain that emerges the following year because the chemicals on its surface have changed and they won’t be recognized as antigens by the body’s B cells.
Immune system problems
When people develop problems with their humoral immunity, they are more susceptible to developing infections and disease. Conditions like HIV directly attack the immune system to make it less functional. Immunity can also be impaired by the use of certain drugs, such as chemotherapy for cancer treatment and drugs used to prepare people for organ transplants. In individuals who have compromised immune systems, aggressive and prompt treatment of any infection is crucial to prevent the body from becoming overwhelmed by something it cannot fight off.
Another problem that can occur with the immune system is autoimmune disease. Normally the system is able to chemically distinguish between substances that are part of the body and those that are not, and will only respond to “foreign” substances. Sometimes, however, the system can mount an immune response to something that is a normal cellular component of the body, treating it in the same way as an invading organism. This causes tissue damage and is responsible for a number of serious diseases such as rheumatoid arthritis, lupus and celiac disease.
The origin of the term
The term “humoral immunity” comes from the fact that this type of immunity is mediated by cells that float in the blood and lymph, or “humours,” of the body. When researchers first began exploring the concept in the 1800s, many of them believed in medical theories dating back to ancient times, which included the idea that the body’s balance was maintained with substances flowing through the body and causing various effects. While the humour theory has since been debunked, it lingers in medical terminology.
