What are genetics and genomics?

Genetics is the study of heredity in which a single gene is examined, and there’s a thorough review of its composition and its functioning(1). A gene is the basic functional unit of heredity(2). Initially, the term ‘gene’ was understood as the ‘unit of inheritance’(3), and it has been assessed that humans have between 20,000 and 25,000 genes(2). 

Genes are made up of deoxyribonucleic acid (DNA), which is the heredity material. The most important characteristic of DNA is that it can make copies of itself, which means it can replicate itself.

Genomics, on the other hand, is the study of all the genes, their functions and the effect they have on the growth and development of the organism(1). Naturally, this also includes the immune system.

What is the connection between genetics and the immune system?

We’ve explored immunity and its importance in our physiology here. The immune response to infections is thought to be influenced by several genetic and environmental factors(5). 

In a study on female twins, it was concluded that 76 % of immune system traits were influenced by heredity and 24 % by environmental factors(6). It was also observed that adaptive immunity traits were influenced more by genetics, whereas innate immunity traits were influenced by environmental factors, such as diet and exposure to infections.

T and B cells are lymphocytes and are part of the adaptive (or antigen-specific) immune response(7). B cells are responsible for humoral immunity, and their activity is marked by release of antibodies, whereas cell mediated immunity depends on the T Cells.

Research has shown that variations in the numbers of T cells were influenced more by genetic factors, whereas the numbers of B cells were shaped by environmental factors(8).

Whether the response of the immune system is innate or adaptive depends on the selective expression of particular genes. Depending on the receptors, the immune cells gauge the surroundings and modify the genes which are encoded by their DNA(9). 

Some genes are turned on to fight the infection, while others are not, and the immune cells have the flexibility to counter the infection as deemed fit by them. There are several mechanisms through which the immune cells deal with the infection(9).

So what?

While we can’t do much about our genetic make-up, we can improve innate immunity through positive lifestyle choices such as a balanced diet and regular physical exercise to keep infections at bay. 

How can genetics help when the immune system is failing?

In rare cases, there are persons who are born with an immune system that does not function well. The unusual mutations that occur prevent immune cells from maturing and children afflicted with this condition sadly do not have a long life expectancy, because they are susceptible to repeated infections.

One mechanism through which these children can be equipped to resist infections is to fight the immunodeficiency. This is done using donor bone marrow cells, which do not undergo the detrimental genetic mutations. In some cases, the individual’s own cells are modified by genetic engineering to rectify the problem(9).

The functioning of the immune system is a very delicately-balanced mechanism which has to fight against environmental intruders and disease-causing micro-organisms or pathogens. At the same time, the body’s immune system should not react abnormally to any of its own cells, which could result in autoimmune disorders . This precarious homeostasis is maintained with the help of genetic and environmental factors(6).

Simply put-

Genetics is not something we can control or manipulate at the individual level; however, to a certain extent, we can influence the innate immune system as it is influenced by environmental factors such as diet. A balanced diet makes it possible to keep nutritional deficiencies at bay and avoiding or quitting smoking would help to strengthen our innate immunity. 

We delve into other aspects of immunity such as gut health and the immune system, inflammation and how lifestyle choices influence the immune system in other articles in this series on immunity.