Body processes

Cross Immunity – Function, Task and Diseases

Cross immunity

People who have cross- immunity are simultaneously immune to another homologous (similar) pathogen when they come into contact with one pathogen. Synonyms are acquired immunity and cross-reaction .

What is cross immunity?

Cross-immunity is directed by a specific immune response against a specific antigen (pathogen). However, the ability to fight off the pathogen must first be acquired through initial contact with this antigen. The immune response to the pathogen is not immediate, but delayed in the form of a specific antigen-antibody reaction.

The cross-reaction only intervenes when the unspecific (natural) immune system fails or the organism is repeatedly attacked. Cross immunity takes a few days or weeks to take effect. With specific accuracy, it is only directed against an attacker (pathogen) and only reacts after renewed contact with the antigen.

Function & task

The natural defense system takes care of pathogens that have managed to penetrate the organism in the form of so-called scavenger cells, which appear as macrophages, neutrophilic granulocytes and monocytes. Proteins that are soluble in the blood and have their own defenses are also included. It is a cellular defense front that is activated and attracted by chemical messengers . In the case of wounds and sources of infection, she is always the first to arrive at the crime scene.

This natural defense is also called non-specific defense because it is not directed against specific antigens like innate immunity or acquired immunity (cross-immunity), but immediately eats up any potentially threatening, unknown and exogenous pathogen. An analysis of the attacker does not take place, just as little as the defense cells remember the type of pathogen. They enclose it with scavenger cells and “throw” it out.

Fungi , viruses , mycobacteria, bacteria and parasites are the uninvited lodgers that keep the immune system active on a regular basis. They often pose a health threat and must be eliminated.

The anatomical barriers are the outer borders such as the skin , mucous membrane , cilia , nasal bunny or the bronchial mucosa, which ward off the roughest attacks from the outside. They render germs harmless. If these anatomical barriers are irritated or injured, pathogens can easily penetrate the weakened organism.

Cross-immunity is not only directed against the original antigen, but also against other, related antigens. If a person falls ill with a bacterial infection, cross-immunity against other related bacteria is possible. The sick person is no longer infected with the bacterial sequelae, since the cross-reaction makes them immune to the causative pathogens. His body’s own defense system develops resistance to a renewed illness.

Diseases & Ailments

Since the immune system often reaches its natural limits, the organism activates the intelligent defense system. B lymphocytes , which form in the bone marrow , take over. They collect in the spleen and the lymph nodes , where they form antibodies against the invading pathogens. The T lymphocytes mature in the thymus and, together with the B cells, form the “specific defence”. This type of immune system also includes cross-immunity because it defends itself against individual, specific pathogens.

The cross-reaction usually defends itself against homologous (similar) pathogens, but can occasionally also act against heterologous (different) antigens. What is special about this process is that the immune system remembers the nature of the attacking pathogen types. In the event of a repeated infection, the organism can react effectively and quickly. However, this form of acquired defense does not set in immediately, but takes a few days or weeks until it takes full effect, as a learning process takes place in the body. This immune protection persists through memory cells ( immunological memory ) for years or even a lifetime.

After this learned process and its implementation, the immune system can become stronger. Vaccinations are also based on this principle . When the vaccine is given, the organism is fooled into believing that it is infected with a special germ, since the vaccine is very similar to the causative agent of the infection in its external properties. However, it is designed in such a way that it does not lead to illness.

The body forms antibodies and remembers them. If an actual infection occurs, the organism immediately deploys its entire arsenal of antibodies to fight the invading pathogen. However, the memory of the immune cells decreases over time, so that a new vaccination is necessary. Tetanus requires three vaccinations, while one vaccination is sufficient for influenza .

Humans are regularly surrounded by viruses and bacteria and they almost always try to penetrate the body’s own defense barrier, but mostly without success. If the body’s defense system does not work as it should, this can result in many complaints and illnesses such as coughs , hay fever , various allergies , fever and a large number of different infectious diseases . A protective effect achieved by antibiotics can lead to miscolonization with resistant pathogens if certain beneficial bacteria are suppressed or killed by the administration of antibiotics. fungi and staphylococcithen spread unhindered and become pathogenic.

Different infectious diseases immunize in different ways. Measles induces lifelong immunity in many people, while it is possible that people who have had scarlet fever once will contract it a second time in their lifetime. In the case of dengue fever , the organism develops protective antibodies against the infecting subtype, but in the event of renewed infection with a dengue virus of the three other subtypes, these have an amplifying effect on the course of the disease and increase the pathogenicity. This infectious disease is an example of the fact that cross-immunity through initial contact with a virus does not always immunize the organism against other, similar types.

Website | + posts

Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.