Genetic influence on immune system

Human leukocyte antigens (HLAs) are specific molecules, antigens, which occur on (almost) all body cells. Everyone has a unique set of these antigens, and these help the immune system determine which cells are your own and which cells are invaders. The typing of these antigens is therefore especially important for organ transplantation. HLA typing can also help identify specific diseases, such as HLA B27, which is known to be closely related to conditions such as Bechterew's disease.

There are two classes of HLA molecules. HLA class 1 molecules are present on every cell and signal to your immune system that it is a body's own cell and not an invader. HLA class 2 stimulates the immune system. HLA molecules are extremely specific to each person. It is therefore especially important in organ transplants to find a donor who matches your HLA type as closely as possible. The recipient's body must think that the new donor organ, like all other organs, is part of his own body. Otherwise, it will reject the new organ.

Infectious diseases are diseases caused by microorganisms such as bacteria, viruses, and fungi. The Covid-19 pandemic has once again shown how serious infectious diseases can be. Other known infectious diseases are HIV-AIDS, hepatitis C and malaria. Much research is being done into the differences between individuals that could predict how severe the course of the disease will be for those individuals. Research has shown that differences in HLA type can influence this. For example, it has recently been shown that there is one type of HLA in which a corona infection is likely to progress worse than in people with another type. In addition to the difference in the course of the disease, there is also a relationship between the HLA type and the risk of infection for various infectious diseases.

Everyone has two copies of each gene, one from your father and one from your mother. This is also the case with the HLA genes. With the HLA genes it is important that the two copies are different from each other. People with two different variations of each HLA gene seem to have a better defense against infections. Many animals unconsciously select their mate through olfactory signals. With these signals they pick up that the partner has a different HLA pattern than themselves. Their offspring will therefore have a varied HLA type. It seems that this is unconsciously also the case with humans. Couples with a difference in the HLA pattern are slightly happier with their partner and want slightly more children than couples where this is not the case.

Since the HLA system was discovered, a lot of research has been done into the relationship between the different types and different diseases. Population studies conducted over the past few decades have identified a long list of human diseases that are significantly more common in individuals with certain HLA alleles. For example, a link has been found in type 1 diabetes, Bechterew's disease, rheumatoid arthritis, and narcolepsy. The mechanism behind this is not yet known. It is possible that the recognition of the body’s own cells is incorrectly done causing parts of your body to be attacked. Another possibility is that these specific HLA types always happen to coincide with other gene variations that are responsible for the genetic predisposition to a disease.