Question

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Immune system is our body defense system against foreign pathogens. Describe how innate and adaptive immunity respond and defend against a novel virus, such as SARS-CoV-2

Answer 1

A key property of the innate immune system is the ability to recognize viruses as ‘foreign’. Viral proteins and nucleic acids are distinguished from cellular counterparts by cellular proteins called pattern recognition receptors .These are proteins present either in the cell cytoplasm or on cellular membranes, where they detect viral components. A series of reactions occur which lead to the synthesis of cytokines, the primary output of the innate defense system.Another key component of the innate response are the so-called sentinel cells: dendritic cells and macrophages present in peripheral compartments such as skin and mucosal surfaces. Sentinel cells patrol the body, seeking signs of infection. Dendritic cells bind cytokines produced by virus-infected cells, and also take up viral proteins released from dying virus-infected cells. They respond by producing more cytokines to amplify the original response.

On the other hand, acquired immunity plays a major role in the responses to re-infection with viruses.The ACQUIRED defense consists of antibodies and lymphocytes, often called the humoral response and the cell mediated response. Antibodies generally bind to virus particles in the blood and at mucosal surfaces, thereby blocking the spread of infection. In contrast, T cells recognize and kill infected cells. A key feature of the adaptive immune system is memory. Repeat infections by the same virus are met immediately with a strong and specific response that usually effectively stops the infection with less reliance on the innate system.