“During the Covid-19 pandemic, the world is unwittingly conducting what amounts to the largest immunological experiment in history on our own children. We have been keeping children inside, relentlessly sanitizing their living spaces and their hands and largely isolating them. In doing so, we have prevented large numbers of them from becoming infected or transmitting the virus. But in the course of social distancing to mitigate the spread, we may also be unintentionally inhibiting the proper development of children’s immune systems.
Most children are born with a functioning immune system with the capacity to respond to diverse types of foreign substances, called antigens, encountered through exposure to microorganisms, food and the environment. The eradication of harmful pathogens, establishment of protective immunity and proper immune regulation depends on the immune cells known as T lymphocytes. With each new infection, pathogen-specific T cells multiply and orchestrate the clearance of the infectious organism from the body, after which some persist as memory T cells with enhanced immune functions.
Over time, children develop increasing numbers and types of memory T cells, which remain throughout the body as a record of past exposures and stand ready to provide lifelong protection. For other antigen exposures that are not infectious or dangerous, a type of healthy stalemate can result, called immune tolerance. Immunological memory and tolerance learned during childhood serves as the basis for immunity and health throughout adulthood.
Memory T cells begin to form during the first years of life and accumulate during childhood. However, for memory T cells to become functionally mature, multiple exposures may be necessary, particularly for cells residing in tissues such as the lung and intestines, where we encounter numerous pathogens. These exposures typically and naturally occur during the everyday experiences of childhood — such as interactions with friends, teachers, trips to the playground, sports — all of which have been curtailed or shut down entirely during efforts to mitigate viral spread. As a result, we are altering the frequency, breadth and degree of exposures that are crucial for immune memory development.”