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Pathogen Recognition Receptors in Immune Signaling

   

Added on  2019-09-22

5 Pages1972 Words422 Views
Disease and Disorders
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Immunity and InfectionIntroductionThe primary role of immune system of the human body is to protect it against diseases or anyother harmful foreign bodies. That fact that our bodies are in constant exposure to the infectiousagents and yet we are able to thwart the infections. It is our immune system that comes into playthat resists these infections. It is one of the most complex systems of the human body that takescare of all other systems such as respiratory system, nervous system etc. So, it is well equippedto neutralize foreign bacteria, parasites, fungi and viruses as these pathogens have the propensityto grow and multiply inside our bodies with destructive consequences (Qiao, 2006). In thefollowing essay, we will try to understand different aspects of immune system, particularly,innate and adaptive immunities. What is their significance and how they work in tandem to fightagainst foreign pathogens. Failing to protect may Spell TroubleEven though its greatly evolved mechanism of identifying and fighting the germs, the immunesystem sometimes seems to be unable to give the protection that is paramount for us. Thiscomplex system in turn relies on specialized elements such as T cells, B cells, macrophagesalong with antibodies and biochemical. All of these units perform their specific tasks, whilecoordinating with each other at the same time. So, if any of these units becomes dysfunctional,there is a possibility that entire immune system can collapse (Lee & Mazmanian, 2010).The Innate Immune SystemThe innate immune system is also known as the first line of defense against the pathogens thatinvades the human body. Most of the encounters that our bodies have with the microorganismsare detected and destroyed and within minutes or hours because innate immunity is at work allthe time. The cells that are involved in innate immune system are neutrophils, monocytes,macrophages and dendritic cells. These important elements start developing during the fetal lifeand mature at different stages of the human life.The neutrophils are stimulated by granulocyte-colony just before birth. They get sharplyincreased in number, however, show weak responses towards bacterial functions andinflammatory stimuli. These deficits are more conspicuous in preborn infants. The monocytesand macrophages are also immature in premature children (Ozinsky et al., 2000). In other words,the innate immune system is relatively dormant at birth due to the fact that a fetus not only had togo through non-shared maternal antigens but also tolerate the significant amount of stress andremodeling taking place during its development. Which is why, the newborn is relativelysusceptible to viral and bacterial infections.
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The Adaptive Immune System The adaptive immune system primarily consists of antibodies and lymphocytes. This immunesystem is often known as humoral response and cell mediated response. As the name suggests,adaptive immunity is about tailoring its response to a particular foreign invader. The cells thatget involved in adaptive immune system are lymphocytes – B cells and T cells. The B cells are produced by the bone marrow, which in turn produce antibodies. The B cellsafter being produced in the bone marrow, move into lymphatic system in order to circulate andpresent throughout the body. Inside this system, the B cells encounter antigens and get matured.The B cells have distinctive antigen-specific receptors according to one’s DNA. So, when anaïve B cell encounters membrane bound anti-body, it divides and forms either a memory B cellor effector B cell. The T cells, on the other hand, differentiate into cells that either participate inlymphocyte maturation or help in killing virus-infected cells (Randolph, 2005).One of the key attributes of the adaptive immunity is its memory. Sometimes a repeat infectionoccurs due to the same virus, then in such a situation it meets with a strong and specific responsebecause of the immune memory. A primary adaptive response may take days to mature, whilememory response shows its effects in hours after infection. The subsets of B and T lymphocytesare responsible for immune memory. The fact that secondary responses are stronger than theprimary ones, the childhood infections, therefore, protect adults and immunity endowed byvaccination could last for years.Coordination of innate and adaptive immune systemsIn general, the ability to produce response in a manner that is virus-specific is a lot dependentcommunication between innate and adaptive immune systems. This particular communicationestablished between the two systems is established by cytokines that help in making cell-to-cellinteractions between dendritic cells and lymphocytes in lymph nodes. This interaction is soimportant that it is impossible for adaptive response to occur without any help of innateimmunity. The discovery of pathogen recognition receptors (PRRs) and dendritic cells allowed us to delvedeeper to expand our knowledge base regarding immune system by connecting innate immunesignaling and adaptive immunity. It provides a fair idea as to how the innate immunity regulatesand shapes our adaptive immune responses. In this the dendritic cells play a crucial role for theimmune signaling network because they are important phagocytic antigen-presenting cells thatknow the onslaught of pathogens via PRRs. This response mechanism is characterized by Toll-like receptors (TLRs) or Nod-like Receptors (NLRs), which is also responsible for activatingnaïve T cell response (Watford, Moriguchi, Morinobu, & O’Shea, 2003).In simple terms, the innate immune system lets the adaptive immune system know when will bethe right time for mounting a defense. It’s being done by making two types of changes on thephagocyte surface that activate adaptive immunity. These changes are also important for theactivation of whole immune system. The phagocytes are also referred to as antigen-producingcells because when it engulfs the invading pathogen, they produce the strands of protein derived
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