Immunity system overview


The human body’s immune system is a complex system that protects one from germs. Normally, in our environment, we are surrounded by millions of bacteria, fungi, viruses, parasites ready to enter our body and make us sick. If not for this system, humans would constantly be getting sick even from the slightest infections.

The immune system is composed of two components: the innate or natural system and the acquired immune system.

Innate system

This system is what we us humans are born with and protect us from germs right from after birth. In our body, we have cells which are important in fighting germs like natural killer cells and macrophages. When bacteria gains entry into our body, it is these cells that play the primary role of ingesting them, and producing chemicals that kill them.

Another form of natural immunity human possess is the skin, mucosa surfaces and some secretions. Normally, our skin is covered by a normal flora of mostly bacteria, and a little bit of fungi. These organisms produce components that destroy pathogenic bacteria that colonize that area.

Concerning secretions, some have organisms that thrive best in basic medium. Usually, the acidic secretions of the skin and the gastric mucosa offer unfavorable conditions for bacteria to thrive. In the respiratory tract, mucosa is lined by cilia which beat in the opposite direction to prevent entry of pathogens to such delicate areas.

Tears, nasal secretions, saliva, and sweat contain enzymes that are capable of destroying certain types of bacteria.  Breast milk also got a numbers of enzymes that boosts the immunity of the neonate against infections.

Acquired immunity

This is immunity which one develops when one is infected. It is usually mediated by lymphocytes. We have two types of lymphocytes, B- lymphocyte and T-lymphocyte. Acquired immunity can also be divided into, cell-adapted immunity and hum oral immunity.

Cell-adapted Immunity

This is a system that is entirely mediated by T-cells. Antigens are usually engulfed by the antigen presenting cells, macrophages or dendrites. After ingestion, they break the antigen and present a small protein component to the T-helper cell. This cell is what will produce cytokines to have an increase in more T-cells and other cells necessary to fight infections. In case of viruses, Cytotoxic T-cells play a key role in eliminating them.

Hum oral immunity

This on the other hand purely involves the B-cells. Antigens become attached to immature cells, and with the help of a T-helper cell nearby releasing cytokines, they mature and release antibodies. Immunoglobulin m is commonly produced during the first immune response. In subsequent infections of the same organism, immunoglobulin g is produced and this lead to fighting of the organism through a number of ways. Antibodies usually form immune complexes with antigens, and then finally activate the complement system that in turn degrades them.


Without the immune system, the human species would have already been wiped uot from the face of the planet.