Charting a Covid-19 Immune Response - The New York Times - 1 views
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Amid a flurry of press conferences delivering upbeat news, President Trump’s doctors have administered an array of experimental therapies that are typically reserved for the most severe cases of Covid-19. Outside observers were left to puzzle through conflicting messages to determine the seriousness of his condition and how it might inform his treatment plan.
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From the moment the coronavirus enters the body, the immune system mounts a defense, launching a battalion of cells and molecules against the invader.
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In severe cases, however, the clash between the virus and the immune system rages much longer. Other parts of the body, including those not directly affected by the virus, become collateral damage, prompting serious and potentially life-threatening symptoms
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On Friday, the president received an experimental antibody cocktail developed by drug maker Regeneron. The next day he began a course of the antiviral remdesivir. Experts say such treatments might be best administered early in infection, to rein in the virus before it runs amok.
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A typical immune response launches its defense in two phases. First, a cadre of fast-acting fighters rushes to the site of infection and attempts to corral the invader. This so-called innate response buys the rest of the immune system time to mount a second, more tailored attack, called the adaptive response, which kicks in about a week later, around the time the first wave begins to wane.
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Eventually, a second wave of immune cells and molecules arrives, more targeted than their early counterparts and able to home in on the coronavirus and the cells it infects.
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If the innate immune system makes early progress against the virus, the infection may be mild. But if the body’s defenses flag, the coronavirus may continue replicating, ratcheting up the viral load. Faced with a growing threat, innate immune cells will continue to call for help, fueling a vicious cycle of recruitment and destruction. Prolonged, excessive inflammation can cause life-threatening damage to vital organs like the heart, kidneys and lungs.
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On Sunday, President Trump’s doctors reported that he had also received a course of dexamethasone, a steroid that broadly blunts the immune response by curbing the activity of several cytokines. Dexamethasone has been shown to reduce death rates in hospitalized Covid-19 patients who are ill enough to require ventilation or supplemental oxygen. But it is far less likely to help and may even harm patients at an earlier stage of infection, or those who have milder disease. Experts say that administering dexamethasone inappropriately, or too soon, could undermine a helpful immune response, allowing the virus to ravage the body.
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At 74 years old and about 240 pounds, Mr. Trump occupies a high-risk age group and verges on obesity, a condition that can exacerbate the severity of Covid-19. Men also tend to have a poorer disease prognosis.