The Role of B Cell Responses in Adaptive Immunity

Providing specific examples, critically evaluate the validity of this statement.

All B cell responses and antibody production to infection, are mechanisms of adaptive immunity’.

B cells, also known as B lymphocytes, are the white blood cells of lymphocyte subtype (Zhang, et al. 2020). They act as the potential immune component of adaptive immune system by producing sufficient number of antibodies. B cells are involved in presenting antigens for which they are also called as the Antigen Presenting Cells [APC], that release the sufficient number of cytokines into the circulation thereby developing adaptive immune system against the microbes and pathogens ta enter into the body. As stated by Sullivan et al. (2019), unlike the others two types of the WBC such as natural killer cells and the T cells, only B cells have the receptors on the cells membranes that are known as the B cells receptors (BCR). These receptors bind to specific antigens that entered into the body thereby initiating adaptive immunes response in the body. the maturation and the origination of B cells occur in the bone marrow in case of mammals. B cells generally situated outside the lymph nodes of the respiratory track, GI track, spleen and the germinal centres (Sullivan et al. 2019). After activation of these cells, they undergo cloning process through which they differentiated into matured B cells which then produce the antibodies that are specific to the antigens presented by the pathogens.

The major function of B cells is to mediate and regulate the antibody mediated immunity [AMU] or humoral mediated immunity [HMI] process against any pathogen (Zhao and Elson, 2018). These two processes occur when B cells identify the antigens on the surface of a pathogen and bind to the antigen through its specific B cell receptor [BCR]. After binding to the BCR, the antigen activates the B cell which then produces specific antibodies that are associated with killing the antigens by initiating the phagocytosis or endocytosis process, thereby protecting body from the adverse impact on bacteria and viruses. evidence suggest that activation of B cells is mediated through the T cells, in which T cell dependent (TD) activation process assists the antigen bounded T cells attached to the site other than BCR of the B cell (Zhang et al. 2020). once the B cells is activated through the T cells it is then transformed into the plasma cell. This transformation occurs due to the changes in the position of the cytoplasm, endoplasmic reticulum and other organelles, which then cause the transcription of organelles into the cytoplasm and cause the secretion of the antibodies into circulation. After the B cell develop the antibodies for the specific antigens it remembers the antigens for future thereby producing the antibody quicker. This is why B cells are considered as the active facilitator of the adaptive immunes system.

As stated by Zhao and Elson (2018.), immune system of the body can be categorised into two major types such as adaptive and innate immune system. The innate immune system is controlled, regulated and performed by a system that is present inside the body. On the other hand, while any pathogens or microbes enter into the body the adaptive immunes response is developed inside the body against the pathogen. B cell act as the important mediator and immune agent in developing specific adaptive immune response to kill the antigen and provide the body with protection against the effect of antigens. The adaptive immunes system is specific to the particular infectious agents. Therefore, not the similar adaptive immune response is devolved for the of all types of pathogens, rather the response is different for each pathogen. B cell is the potential element of the adaptive immunes system that is associated with producing the high number of specific antibodies that are relevant to kill and protect against the entered pathogens or antigens insides the body.

As mentioned by Nus et al. (2017), There are many sequences of events that occur synchronously during the activation if B cells. In this process the first step is the entry of a pathogen or microbe into the body. After the entry of pathogen, a protein is located on the surface of the pathogen in which the major histocompatibility complex (MHC) class molecules are situated. As stated by Zhao and Elson (2018), the protein that is located on the surface of the infectious agent is known as the antigen. The activation of B cells is caused through the binding of the antigen to the BCR which then causes the B cell to engulf the antigen that then cause the degradation of the pathogen thereby protecting the body.

In the next stage of the activation process of the adaptive immune system, the antigen of the MHC site presented on the surface of the antigen presenting cells are now recognised by the T cells. In this process the activation of B cells is occurred through the T cell dependent (TD) activation process in which the CD 28 receptor of T cell bends to the B7 receptor of the antigen presenting cells [APC] . Through this process the naïve or memory T cells become activated, which are now converted into the active T helper cells that undergoes the process of Clonal Replication thereby increasing in number. At this time the activation of B cells occurs through detecting the antigens in its BCR which then produce the cytokines and antibodies to engulf ad degrade the antigen. However, the activation of B cells does not happen until the cells is involved in brushing against B cells and then bind to the MHC molecule along with CD28-B7 site. At this binding site, the T helper cells produce and secrete cytokines, the chemical messengers that are detected by the B cell thereby causing the initiation of endocytosis process through which the antigens are taken up by the B cells and then degraded into inactive molecules. After activation of B cells, they undergo the cloning process and produce large number of clones which then go to the plasma cells or the B memory cells in which they secrete specific into the tissues and organs through the blood flow. This entire process is known as the adaptive immune response in which body doesn’t have any pre-prepared immunes system but after the entry of the pathogens and microbes into the circulation, the B cells recognise the protein on the surface of the pathogens and the synchronous process of the activation of B cells and T helper cells is happened.

After the activation, B cells are involved into the two-stage differentiation process. Through undergoing these two-stage process, there is production of large number of plasma blasts that are associated with providing the immediate protection to the memory B cells and the plasma cells (Nus et al. 2017). The first stage is called as the extrafollicular response that happens on the lymphoid follicle. In this stage the activated B cells are proliferated that are then differentiated into plasmablasts that are involved in the production of the poor antibody class (class of igm). In the next stage the active B cells enter into the lymphoid follicle that then form the germinal centre (GC). GC has the specialised and approved microenvironment in which B cells can undergo huge proliferation and the proper immunoglobulin class switching which then produce the long lives plasma cells and high-infinity memory B cells which then produce the potential antibody class such as IgE, IgA and IgG. Through developing these antibodies B cells are associated not only with destroying the antigens or proteins of pathogens thar enter inro the body but also maintain proper balance between innate and adaptive immune system.

Mature B cells generally present in the bone marrows and the plasma cells which activate when an antigen binds to its receptor site (BCR) (Rizzetto et al. 2018). Through formation of GC, the B cell undergoes huge proliferation which is associated with developing the mature plasma and B memory cells, there are associated with developing strong antibodies and cytokines that are associated with developing adaptive immune system inside the body. There are five major types of antibodies that B cells produces to develop the specific immune response inside the body against particular pathogens.

IgE: These antibodies are produced by B cells with the help of the T helper cells while any worm infects the body. While the protein of the pathogen enters into the body and is recognised by the B cells and T cells, these cells undergoes the activation process, which then cause production of this types of antibody.

IgA: Generally, B cell rarely form these antibodies as they present in the body as the part of innate immune system. they play active roles in maintain neutral and perfect internal environment inside the body such as maintaining temperature, sugar level and response against fever

IgG: This is one of the most potential antibodies that are formed by the mature B cells. The B cells produce these antibodies while the body is infected by any virus or bacteria. Some of these kinds of antibodies are so strong that can enter into the placenta and destroy the foetus as it detects the foetus as the antigen if the blood group of foetuses and the mother is different.

IgM: this is a weak category of antibody that is involved in providing poor response to the pathogenic attacks. During the middle of the activation phase B cells form these antibodies, which are then associated with the other mature forms of antibodies that develop the strong immune system inside the body.

From the overall discussion, it can be stated that the abovementioned statement” All B cell responses and antibody production to infection, are mechanisms of adaptive immunity’”, is high justified as B cells play an important role in developing the adaptive immune response in the body against the pathogens. B cells act as the potential immune facilitators that undergo the activation process during the adaptive immune system thereby becomes mature B cells which are associated with production of large number of cytokines and antibodies. B cells have the receptor, the BCR that recognises specific protein on the surface of the pathogen and binds to it through lock and key process. among all kinds of lymphocytes such as T cells, B cells and natural killer cells, only B cells have the receptors [BCR] for antigens on its surface which make it able to take crucial part in detecting the MHC factor on the surface of pathogen and then bind to it to produces the specific cytokines as well as antigens which then assist that B cells to destroy the antigen through initiating the endocytosis or phagocytosis process.

Reference list:

Hong, S., Zhang, Z., Liu, H., Tian, M., Zhu, X., Zhang, Z., Wang, W., Zhou, X., Zhang, F., Ge, Q. and Zhu, B., 2018. B cells are the dominant antigen-presenting cells that activate naive CD4+ T cells upon immunization with a virus-derived nanoparticle antigen. Immunity, 49(4), pp.695-708.

Nus, M., Sage, A.P., Lu, Y., Masters, L., Lam, B.Y., Newland, S., Weller, S., Tsiantoulas, D., Raffort, J., Marcus, D. and Finigan, A., 2017. Marginal zone B cells control the response of follicular helper T cells to a high-cholesterol diet. Nature medicine, 23(5), pp.601-610.

Rizzetto, S., Koppstein, D.N., Samir, J., Singh, M., Reed, J.H., Cai, C.H., Lloyd, A.R., Eltahla, A.A., Goodnow, C.C. and Luciani, F., 2018. B-cell receptor reconstruction from single-cell RNA-seq with VDJPuzzle. Bioinformatics, 34(16), pp.2846-2847.

Sullivan, J.L., Bagevalu, B., Glass, C., Sholl, L., Kraft, M., Martinez, F.D., Bastarrika, G., De-Torres, J.P., San Jose Estepar, R., Guerra, S. and Polverino, F., 2019. B Cell–Adaptive Immune Profile in Emphysema-Predominant Chronic Obstructive Pulmonary Disease. American journal of respiratory and critical care medicine, 200(11), pp.1434-1439.

Zhang, F., Gan, R., Zhen, Z., Hu, X., Li, X., Zhou, F., Liu, Y., Chen, C., Xie, S., Zhang, B. and Wu, X., 2020. Adaptive immune responses to SARS-CoV-2 infection in severe versus mild individuals. Signal transduction and targeted therapy, 5(1), pp.1-11.

Zhao, Q. and Elson, C.O., 2018. Adaptive immune education by gut microbiota antigens. Immunology, 154(1), pp.28-37.

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