Flu causes paradox in the immune system

US researchers say they have discovered why the flu makes people susceptible to deadly pneumonia. This finding may explain the fact that ' death from the flu ' is not caused by the flu virus.

Many people who are considered ' dead from influenza ' actually die from pneumonia due to secondary infections such as Streptococcus pneumoniae, Staphylococcus aureus .

Dr. Jane Deng at the University of California, Los Angeles and colleagues reported their findings in The Journal of Clinical Investigation (Journal of Clinical Research) . They hope what they find will lead to the treatment of influenza patients by curing pneumonia after the flu and preventing the influenza virus from weakening the immune system.

Signal response

Many deaths from pneumonia due to secondary infection (Photo: Kim Kyung-Hoon / Reuters)

So far, it is not clear why flu causes people to become sensitive to secondary infections that cause pneumonia. To understand this, scientists conducted research on mice, targeting the Interfron signaling molecule (type 1 IFNs). Normally, the interferons produced by the immune system to limit viral replication and control infection.

But the researchers found that patients with the flu became more sensitive to the bacteria that cause pneumonia, due to their weak immune response .

Factors that mobilize neutrophil to the sites of infection decrease. Neutrophils are cells located in the center of the original anti-bacterial immune response.

Immunologist and microbiologist Newcastle University, Professor Richard Barry, says it is a paradox because interferon destroys certain genes that stimulate the growth and adhesion of bacteria and at the same time the gene loses its ability. stimulates neutrophils.

" When you have the flu and are so serious that secondary infections occur, the genes needed to produce neutrophils are inhibited. Viruses and interferon are no longer able to make the body produce," he said. white blood cells '.

Overwhelmed

Barry explained why the secondary infection of the flu could be fatal as follows:

" Bacteria through the throat and into the lungs where they are not normally present " - he said - " They will be" swallowed up "by macrophages and leukocytes , but in this case In contrast, the bacteria that cause pneumonia can overwhelm those cells because they are too much.

Previous studies have shown that almost 50 of the 100 million people who died in 1918 by the ' Spanish ' flu pandemic in 1918 were due to the secondary ' super infection ' of Streptococcus pneumoniae pneumonia.

Professor Barry judged that the antibiotics of the past century could not be protected. Unfortunately, the increasing number of antibiotic greases has made the task of controlling pandemic particularly difficult.