The human respiratory system has its own defenses that help the body fight viruses that cause colds.
New research published in the journal Cell Press Blue shows that the nostrils play a far more active role in the body’s first line of defense than previously thought. Scientists have found that the nasal cavity is not only a filter for particles and bacteria, but also a launch point for an immune response that can stop viruses before they penetrate deep into the respiratory tract.
The study involved volunteers who received small doses of viruses that mimic the common cold, administered directly into their noses. Scientists monitored changes in mucus, epithelial cells, and immune molecules in the nasal cavity. They found that during the early stages of infection, numerous defensive proteins and molecules are activated, preventing viruses from multiplying effectively and penetrating deep into the body. These include interferons—special proteins produced by cells that suppress viruses—as well as other immune signaling molecules.
One of the main findings is that the immune response in the nasal passages can be specific to different viruses. This means that mucosal cells can ‘recognize’ certain pathogens and quickly activate the molecules most effective at fighting them. This local response acts as a barrier, preventing the infection from spreading to the lungs and other parts of the respiratory system.
The study authors note that this may help explain why some people experience milder colds—or even no symptoms at all—despite being exposed to the virus. A strong local immune response in the nasal cavity can limit viral replication at an early stage, preventing it from developing into a more severe infection.
These results also help explain why routine nasal hygiene measures, such as saline rinses, can reduce the likelihood of developing symptoms or ease their severity. Cleaning the nostrils helps remove some viruses and maintain optimal conditions for the local defense mechanisms to function effectively.
