Question

Research on the human immune system and its resistance capabilities considering the COVID -19 Virus.

Answer 1

Answer:

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Explanation:

Viruses are obligatory intracellular microorganisms that use components of the nucleic acid and protein synthetic machinery of the host to replicate and spread. Viruses typically infect various cell types by using normal cell surface molecules as receptors to enter the cells. After entering cells, viruses can cause tissue injury and disease by any of several mechanisms. Innate and adaptive immune responses to viruses are aimed at blocking infection and eliminating infected cells. Infection is prevented by type I interferons as part of innate immunity and neutralizing antibodies contributing to adaptive immunity. Once infection is established, infected cells are eliminated by NK cells in the innate response and CTLs in the adaptive response.

1. Innate Immunity to Virus

The principal mechanisms of innate immunity against viruses are inhibition of infection by type I interferons and NK cell–mediated killing of infected cells. NK cells kill other cells infected with a variety of viruses and are an important mechanism of immunity against viruses early in the course of infection, before adaptive immune responses have developed (Figure 3a).

2. Adapted Immunity to Virus

Adaptive immunity against viral infections is mediated by antibodies, which block virus binding and entry into host cells, and by CTLs, which eliminate the infection by killing infected cells. Antibodies are effective against viruses only during the extracellular stage of the lives of these microbes. Viruses may be extracellular early in the course of infection, before they infect host cells, or when they are released from infected cells by virus budding or if the infected cells die. Antiviral antibodies bind to viral envelope or capsid antigens and function mainly as neutralizing antibodies to prevent virus attachment and entry into host cells. Elimination of viruses that reside within cells is mediated by CTLs, which kill the infected cells. The principal physiologic function of CTLs is surveillance against viral infection. Most virus-specific CTLs are CD8+ T cells that recognize cytosolic, usually endogenously synthesized, viral peptides presented by class I MHC molecules (Figure 3b).