BIO226 | The Functions of B Cells and Cytotoxic Cells In Fighting Infe

Introduction

The immune system produces immune responses following entry of pathogens/foreign substances into the body. The paper will give a comparison and contrast of the immune responses of the body to bacterial and viral infections and the functions of the innate immune system in fighting viral and bacterial infections. The paper will also explain the functions of B cells and cytotoxic cells in fighting infections.

Immune responses of the body to viral and bacterial infections

Similarities

Both adaptive and innate immunity systems trigger immune responses to both viral and bacterial infections. For both instances of immune responses, antibodies are always involved (Nicholson, 2016).

Differences

Body’s immune response to bacteria infections involve responses to intracellular pathogens because bacteria live outside the host cells. This makes them not to be easily attacked by the components of the immune system. The mechanisms involved are complement-mediated lysis, adaptive immunity and phagocytosis. On the other hand, the body’s immune response to viral infections involve responses to intercellular pathogens because viruses live inside the cells of the host. In this instance, the immune system uses three major methods namely; interferons, cytotoxic T cells and antibodies (Greenwood, Slack, Barer & Irving, 2012). In viral infections, the immune system of the body recognizes the cells infected with viruses via the viral epitopes presented by MHC molecules.

Role of the innate immune system in fighting viral and bacterial infections

The innate immune system has barriers like skin, cilia, and body hair used in the prevention of the spread of infections. It has defense mechanisms like mucous, secretions, tears, sweat, saliva, gastric acid and bile which fight back any bacteria or virus that gets into the body. It also involves general immune responses like inflammation and complement system (Deretic, Saitoh & Akira, 2013).

Role of B cells in fighting infections.

B cells are types of WBCs that protect the body against infections through humoral immunity. In an immature form, B cells circulate in the lymphatic system and bloodstream to defend the body against pathogens. Once they recognize an antigen on the surface of a virus or bacterium, they often get activated and move to the lymph nodes or spleen where infections are fought.  On the lymph nodes or spleen, the B cells rapidly multiply into memory and plasma B cells. The plasma B cells them form and produce antibodies which disable the antigen by coating or binding to it (Abbas, Lichtman & Pillai, 2014). 

Role of cytotoxic T cells in fighting infections

The cytotoxic T cells recognize viral epitopes on the cell membrane of virus-infected body cells using T cell receptors (TCRs) and release cytotoxic factor that kills all the virus-infected cells. The TCRs enable the cytotoxic cells to monitor all body cells and prepare for the destruction of any cell that seems to pose a threat to the host (Abbas, Lichtman & Pillai, 2014). 

Conclusion 

Bacteria are intracellular pathogens while viruses are intercellular pathogens. In bacterial infections, methods such as complement-mediated lysis, adaptive immunity and phagocytosis are used while in viral infections the immune system uses methods like interferons, cytotoxic T cells and antibodies. 

References

Abbas, A. K., Lichtman, A. H., & Pillai, S. (2014). Basic immunology: functions and disorders of the immune system. Elsevier Health Sciences.ews Immunology, 13(10), 722.

Deretic, V., Saitoh, T., & Akira, S. (2013). Autophagy in infection, inflammation and immunity. Nature Reviews Immunology, 13(10), 722.

Greenwood, D., Slack, R. C., Barer, M. R., & Irving, W. L. (2012). Medical Microbiology E-Book: A Guide to Microbial Infections: Pathogenesis, Immunity, Laboratory Diagnosis and Control. With STUDENT CONSULT Online Access. Elsevier Health Sciences. 

Nicholson, L. B. (2016). The immune system. Essays in biochemistry, 60(3), 275-301