A recent study published in the British journal Nature by American researchers found that upper respiratory organs such as the nose are key "training grounds" for immune cells to remember invading pathogens, which enables immune cells to resist future microbial like attacks. The research results are of great significance for the development of mucosal vaccines for upper respiratory tract and other diseases. To better understand how immune cells in the upper respiratory tract interact with pathogens, researchers from institutions such as the La Jolla Institute of Immunology in the United States collect nasopharyngeal swab samples from approximately 30 healthy adults every month for over a year to observe changes in their immune cell populations over time. They found a large number of immune cells in these samples, including cells with immune memory. There is a germinal center located in the adenoid of the immune organ at the end of the nasal cavity. The germinal center is a short-lived organizational structure formed when the body experiences an immune response to antigen stimulation. It serves as a "training camp" in immune tissue and is a place where immune cells learn to produce effective antibodies. It is generally believed that the germinal center of adenoids is only active during acute infection or immune phase. But the researchers found that even if participants did not report discomfort, the germinal centers of the adenoids were active, and the germinal centers of the adenoids were active in all age groups of participants, overturning the previous understanding of adenoid atrophy and inactivation in adulthood. This discovery also poses a challenge for subsequent research, namely that if the immune system remains active in the upper respiratory tract, pre-existing antibodies may limit the protective effect of intranasal vaccines. (New Society)