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Why Does the Immune System Not Recognize the Normal Flora of Microbes As Antigen?


Microbes are living things found in tiny sizes and cannot be found in bare eyes. Microbes live in the human body, water, air, and soil. The human body has millions of microbes to live in, known as microorganisms. The functions of the normal flora of microbes include substrate digestion, producing vitamins by stimulating cell maturity, and stimulating the immune system by colonizing the resistance. On the other hand, the antigen works as a substance that makes the body respond by its immune system against that substance. Antigens include bacteria, chemicals, viruses, toxins and other substances from the external. Eventually, the normal flora of microbes has no harmful connection causing to the body like an antigen. Therefore, it can be the reason why the immune system does not recognize the normal flora of microbes as antigen (Callieri et al., 2018).


There are many reasons why the immune system does not recognize microbes as antigens. The main reason is that the cells are found in lymph nodes throughout the body, they may offer a way of suppressing a variety of autoimmune diseases. Moreover, dendritic cells display the antigens which further put the immune system at ease. Due to this reason, immune system’s T cell does not recognize microbes.

Apart from this, the immune system is the ability of a human body that prevents, defends and eliminates unknown foreign materials and some abnormal cells that are harmful to the human body. The harmful external materials inside the body or with an attempt to access are viruses, parasites, bacteria, toxins, carcinogens, germs, fungus, and pollution.

When the body senses foreign substances, the immune system works to recognize those and get rid of those. However, in case of normal flora of microbes cannot be recognized they are living in other living organisms which are not recognized by the immune system. Any parts of the body like pancreas are sheltered outside the environment of the immune system where these normal flora lives and this puts the overall immune system at ease. The majority of normal flora is known as bacteria which is hard to recognize by the immune systems. Due to these possible surface areas, they cannot be easily recognized.

The immune system is a functional system, not an organ system. Normal flora is known as microorganisms to live on another living organism (Sarmah et al., 2018). These microorganisms live on inanimate objects without any disease. Somenormal floras are microorganisms that live on the surface within the anatomical regions of the body. Normal flora provides benefits, and the effects are found in the oral cavity, intestinal part, skin, and the vaginal epithelium. It prevents colonization by pathogens competing for the required nutrients. This can be another cause that the immune system refuses the normal flora of microbes as antigen (Kogut et al., 2020).

It is the immune system that always distinguishes between the normal and the foreign objects entering into the body by small proteins known as antigens on the surface of the cell. In some body parts like the pancreas, cells are known as antigens as a normal neighbor in the immune system easier. Those antigens are on the alert to the immune system’s T cells learning to attack off-limits. T cells ignore and tolerate the normal intestinal tissue. T cells are critical components related to the adaptive immune system with a capacity to recognize and eliminate the external microbes that attack the human body (Zhang et al., 2019). These are the key reasons. Besides, the immune system works for the distinction between the own cells of the body and the pathogens. It protects the body from the disease and should recognize and attack the pathogens by not causing harm to its own cells. T cells play an important role being the important cell type of the immune system. For the living of many bacterial communities in the body, the human body delivers different environments (Callieri et al., 2018).


The human body is termed as host by scientists, and the positive host-microbe relationship is mutuality. The benefits are received from both microbe and the host through mutualism. According to scientists, ulcers are developed among the people colonized by H. pylori. The microbiologists suggest considering H. pylori in the stomach as normal flora. It can be the reason also behind immune system does not recognize the normal flora of microbes as antigen.

List of References:

Callieri, C., Eckert, E. M., Cesare, A. D., & Bertoni, F. (2018). Microbial communities. Encyclopedia Ecol, 1, 126-134.

Kogut, M. H., Lee, A., & Santin, E. (2020). Microbiome and pathogen interaction with the immune system. Poultry Science, 99(4), 1906-1913.

Sarmah, P., Dan, M. M., Adapa, D., & Sarangi, T. K. (2018). A review on common pathogenic microorganisms and their impact on human health. Electronic Journal of Biology, 14(1), 50-58.

Zhang, C. X., Wang, H. Y., & Chen, T. X. (2019). Interactions between intestinal microflora/probiotics and the immune system. BioMed research international, 2019.


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