Influenza and the Immune System

Proboost - Cold and Flu preventionThe Influenza virus is one of the most common causes of respiratory tract infections. It is responsible for 3-5 million clinical infections every year and 250,000-500,000 deaths per year.

Commonly known as the flu, the symptoms of influenza virus infections include nausea, vomiting, fever/chills and diarrhea in some cases. It can also progress to viral pneumonia or allow secondary bacterial pneumonia. It is transmitted between patients through the air, by coughs, sneezes and also through contact with contaminated secretions. Airborne vectors are considered the most common cause of most infections and frequent hand washings have been shown to be the most successful way to reduce the risk of infection.

The immune system plays a critical role in protecting the body from the influenza virus, and the thymus is at the center of this action. Intracellular, innate sensing of influenza virus infection requires pattern recognition of the viral RNA, the viral’s genetic material. Infected cells recruit and present viral particles to a class of immune cells known at dendritic cells. Dendritic cells acquire viral particles and present those to CD4+ and CD8+ T cells, which mature in the thymus. CD8+ T cells are able to target infected cells and activate their self-destruction, destroying the virus also.

Additionally, natural killer cells are able to recognize antibody-bound infected cells and lyse these cells, in a process known as antibody-dependent cell cytotoxicity (ADCC).  CD8+, CD4+ and natural killer T-cells mature in the thymus and a critically dependent on that process in order to recognize foreign invaders.

Beyond its critical role in clearing influenza infections as quickly as possible, the thymus performs the crucial role of guarding against future infections. By automatically producing antibodies against foreign antigens through B-cell mediated immunity, T-cell mediate immunity also contributes to so-called, “heterosubtypic immunity”. This type of immunity allows the body to respond to mutations in virus strains and mount a proper defense.