Immune System Genetics

The immune system is the strongest defense the body has against infectious diseases that are caused by microorganisms. In order to protect the body, this system has two types of defenses. The first defense the immune system has is called innate immunity. This immunity consists of the physical barriers such as the skin along with special cells known as macrophages, which devour infectious organisms. If the first defense is not effective in repelling these viruses and bacteria, a second and more powerful defense is hence activated. This defense is known as the adaptive immunity.

Adaptive Immunity uses specialized cells known as B cells and T cells. These cells circulate the bloodstream in the body and act as security guards in search for any infectious cell or virus. Once, more specifically, the B cells have tracked down an infectious agent, they release important molecules called immunoglobulins or antibodies. These molecules attach to the infectious agents and send signals to other cells, such as the macrophages, to come and kill the infectious agent. Antibodies are all not the same and their genes contain many types of receptors. These antibodies are genetically diverse.

Antibody diversity occurs during its production in the bone marrow along with B cells. In the bone marrow, these antibodies go through a process known as somatic recombination. During this process, different gene segments are randomly chosen from a small gene pool. These gene segments are known as the V, D, and J gene segments. An antibody has two sections: the light chain and heavy chain. The V and J segments code for the light chain while V, D, and J segments are needed to encode for the heavy chain. These genes are assembled by joining the genes ends together. At this point the DNA is looped, degraded, and spliced in order to join the segments. This same process applies to both light and heavy chain production. Once the segments have been assembled, it can start to encode for a functional antibody.

Because the random genes that were chosen were from a gene pool, the genes are given room to produce millions of combinations due to the addition or deletion of nucleotides during somatic recombination. This strengthens the diversity of antibodies. These molecules will then have a specialized receptor that will seek a certain infectious agent in the body and target it for its death in order to relieve the body from sickness.