Over-reactive immune system kills young adults during pandemic flu

Another reason to get a flu shot (especially young adults)…….

From the December 5, 2010 Eureka news alert

On November 19, Jason Martin returned to the Medical Intensive Care Unit (MICU) at Vanderbilt University Medical Center for the first time since he nearly died there during last year’s H1N1 flu pandemic. The tall and burly Warren County, TN, ambulance worker – a 30-year-old, father of three young children – broke down and hugged some of the nurses he recognized.

“I got sick on September 12 and didn’t come out of it for the next 20 days. I am just so grateful I came through,” Martin said, wiping his eyes.

Martin was among the first wave of critically ill middle Tennesseans, hit hard by the H1N1 flu pandemic in late 2009. A hallmark of pandemic flu throughout history, including the H1N1 pandemic, has been its ability to make healthy young and middle-aged adults seriously ill and even kill this population in disproportionate numbers.

In a paper published Dec. 5 in Nature Medicine, Fernando Polack, M.D., the Cesar Milstein Associate Professor of Pediatrics at Vanderbilt, and colleagues in Argentina and Nashville provide a possible explanation for this alarming phenomenon of pandemic flu. The study’s findings suggest people are made critically ill, or even killed, by their own immune response…

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“We have seen this before. Where non-protective antibody responses are associated with an immune-based disease in the lung,” Polack said.

Polack has previously published evidence that a first-line immune response, primed by an imperfect antibody, can overreact in a violent and uncontrolled fashion. Patients die from lung damage inflicted by their own immune system. A molecule called C4d, a product of this biochemical cascade (the complement system), is a marker for the strength of the response.

In adults who died during the 2009 H1N1 pandemic, high levels of C4d in lung tissues suggest a massive, potentially fatal activation of the complement system.

Pulmonary and critical care physician, Todd Rice, M.D., assistant professor of Medicine at VUMC, has seen people killed by the “exuberant” and uncontrolled response of the immune system in other diseases – like sepsis….

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While many questions remain, one thing is clear: the H1N1 vaccine offers protection. Patients who died were overwhelmingly unvaccinated. Many fell ill before a vaccine was even available. [Editor Flahiff’s empahsis]