Scientists have long believed that a newborn's immune system is an immature version of the adult immune system, but a new study from Cornell University shows that newborns' T cells perform better than adults at fighting a variety of infections. The results help shed light on why adults and infants respond differently to infection and pave the way for controlling T cell behavior in treatments.
The research results were published in the journal Science Immunology on February 23 and were co-led by Brian Rudd, associate professor in the Department of Microbiology and Immunology, and Andrew Grimson, professor in the Department of Molecular Biology and Genetics at Cornell University.
Adult T cells perform better than neonatal T cells at recognizing antigens, forming immune memory, and responding to repeated infections, leading to the belief that infant T cells are simply weakened versions of adult T cells. But during the COVID-19 pandemic, many people were surprised that babies were not sick, calling into question this long-held belief.
Researchers interested in understanding these age-related differences found that neonatal T cells engage a part of the immune system that does not require antigen recognition: the innate part of the immune system. While adult T cells employ adaptive immunity to recognize and then fight specific germs, neonatal T cells are activated by proteins associated with innate immunity.
Brian Rudd said: "Our paper shows that neonatal T cells are not damaged, they are just different from adult T cells, and these differences may reflect the types of functions that are most useful to the host at different stages of life."
Neonatal T cells can participate in the innate part of the immune system. This allows neonatal T cells to do something adult T cells cannot: respond at the earliest stages of infection and defend against a variety of unknown bacteria, parasites and viruses.
"We know that neonatal T cells are less protective than adult T cells against repeated infection with the same pathogen. But in fact, neonatal T cells have a greater ability to protect the host from earlier infections," Rudd said. "So it's impossible to say that adult T cells are better than neonatal T cells, or neonatal T cells are better than adult T cells. They just have different functions."
In follow-up research, Rudd wants to study neonatal T cells that persist into adulthood. "We wanted to understand how changes in the relative numbers of neonatal T cells affect adult susceptibility to infection and disease outcome," he said.