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Physical exercise has a positive effect on the immune system and depending on the frequency and intensity, the pathogenic effects of diseases caused by bacteria and viruses are moderated. [103] Immediately after intense exercise there is a transient immunodepression, where the number of circulating lymphocytes decreases and antibody production ...
Hepatitis C Virus Life Cycle. The mammalian immune system has evolved complex methods for addressing and adapting to foreign antigens. At the same time, viruses have co-evolved evasion machinery to address the many ways that host organisms attempt to eradicate them.
Viral disease is the sum of the effects of viral replication on the host and the host's subsequent immune response against the virus. [3] Viruses are able to initiate infection, disperse throughout the body, and replicate due to specific virulence factors. [2] There are several factors that affect pathogenesis.
These receptors promote virus-antibody internalization by the immune cells, which should be followed by the virus destruction. However, the virus might escape the antibody complex and start its replication cycle inside the immune cell, avoiding the degradation. [5] [25] This happens if the virus is bound to a low-affinity antibody.
An immune response is a physiological reaction which occurs within an organism in the context of inflammation for the purpose of defending against exogenous factors. These include a wide variety of different toxins, viruses, intra- and extracellular bacteria, protozoa, helminths, and fungi which could cause serious problems to the health of the host organism if not cleared from the body.
This is known as "escape mutation" as the viral epitopes escape recognition by the host immune response. These persistent viruses evade immune control by sequestration, blockade of antigen presentation, cytokine resistance, evasion of natural killer cell activities, escape from apoptosis, and antigenic shift. [158]
Although the host may not be experiencing symptoms, the virus can still be passed on to others. It is also possible for the infection to become symptomatic after this incubation period. Whether the host is showing symptoms or not, opportunistic infections can take advantage of the weakened immune system and cause further complications. [20]
A representation of the cholera epidemic of the 19th century. For thousands of years mankind has been intrigued with the causes of disease and the concept of immunity. The prehistoric view was that disease was caused by supernatural forces, and that illness was a form of theurgic punishment for "bad deeds" or "evil thoughts" visited upon the soul by the gods or by one's enemies. [8]