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Module 4 MIC SLP

The human body is often under attack from different pathogens that try to invade it and for those already inside attempt to infest it. However, the body has a defensive mechanism to protect itself against such attacks known as the immune system. It is a system covering the whole body and consists of organs, cells and tissues that have all evolved and gained the defensive capacity against harmful microbes. The immune system functions by initially recognizing foreign antigens, a job well done by antigen-presenting cells, abbreviated as APC, and they are in two forms, either the macrophages or the dendritic cells.

Upon exposure to a pathogen, for example, Mycobacterium tuberculosis the body’s immune system recognizes the antigens on the foreigner’s bodies, which are known as major histocompatibility complex proteins. At this point, the B cells are signaled by the APC, which leads to a proliferation process that releases antibodies. The antigens on the body surfaces of the pathogens combine with the antibodies from the B cells, which is yet another signal for macrophages to attack the pathogens via phagocytosis (Singh and Kiran 154). In case the body is under attack by bacteria, the antibodies still combine with antigens on the pathogens’ surfaces. However, they do not signal macrophages, but serum proteins, known as complement, combine with the stationary pathogenic antibodies. This process is followed by the complement destroying the pathogens by drilling holes through their surfaces and ultimately eliminating them. In case the pathogens, for example, bacteria, have infected the human body, the antibodies, upon combining with the antigens on the surfaces of the infectious microorganisms, signal the macrophages to destroy the infected cells. The immune system has a unique way of distinguishing pathogenic and nonpathogenic microorganisms, for example, Escherichia coli, which involves recognition of Pathogen-Associated Molecular Patterns, abbreviated as PAMPs. If a microorganism lacks the PAMPs, the immune system does not react towards it harshly, for example, by phagocytosis (Vance, Ralph, and Daniel 11). An example of a PAMP is the presence of lipid A on the outer surface of Mycobacterium tuberculosis, and the immune system reacts by destroying the foreign organism. Escherichia coli lacks a PAMP and is part of the normal flora of the human gut as such the immune system does not react against it.

The body’s immune system functions in two major ways, which are innate and adaptive modes. The innate system is quicker than adaptive as it reacts immediately the body is under attack by various mechanisms such as release of mucus, and formation of inflammations among other means of defense. Hence, the system would react by activating innate system upon the introduction of a pathogenic microbe for the first time into a body. However, upon failure of the innate system, the body switches to adaptive mechanism, which takes more time to activate. The key difference between the two systems is that innate one is general and prevents the entry and spread of pathogens while adaptive mode targets only the foreign microbes. Adaptive system forms mechanisms that target the invading microorganisms through antibodies, which the body directs towards the pathogenic antigens, and the rest of the destruction process follows.

When a body is exposed to Mycobacterium tuberculosis, which is the causative agent of tuberculosis, it activates the adaptive immunity system (Informed Health Online Web). Unfortunately, the process of defending itself against the bacteria is slow, but eventually, it gets the job done. Another unique measure related to adaptive immune system is the storage of the defensive path memory. When the body is exposed to the same pathogens, for instance after two years, the body recalls the defensive path and activates it quickly since the antibodies are already in the system.

Works Cited

Informed Health Online. How do the innate and adaptive immune systems work together? National Center for Biotechnology Information, 2012. Web. 23 November 2013.

Singh, Kiran and Kiran, Kapoor. Introductory Microbiology. Jaipur: Global Media, 2010. Print.

Vance, Russell, Ralph, Isberg, and Daniel, Portnoy. “Patterns of Pathogenesis: Discrimination of Pathogenic and Non-Pathogenic Microbes by the Innate Immune System.” Cell Host Microbe 6.1 (2009): 10-21.