Immune system works differently but effectively in babies

A research published in the journal Science Immunology on 23 February 2024 reveals that newborns' T cells - white blood cells that protect from disease -  outperform those of adults at fighting numerous infections. Adult T cells surpass newborn T cells in tasks such as antigen recognition, immunological memory formation, and response to recurring infections. This had led to the assumption that infant T cells were weaker than adult T cells. However, the COVID-19 pandemic revealed a surprising lack of illness in infants, challenging the assumption. The research co-led by Brian Rudd, associate professor of microbiology and immunology, and Andrew Grimson, professor of molecular biology and genetics from Cornell University, showed that newborn T cells are not deficient: Instead, they are involved in a part of the immune system that does not require antigen recognition: the innate arm of the immune system. While adult T cells use adaptive immunity – recognising specific germs to fight them later ­– newborn T cells are activated by proteins associated with innate immunity, the part of the immune system that offers rapid but nonspecific protection against microbes the body has never encountered. “Our paper demonstrates that neonatal T cells are not impaired, they are just different than adult T cells and these differences likely reflect the type of functions that are most useful to the host at distinct stages of life,” Rudd said. Neonatal T cells can participate in the innate arm of the immune system. This enables newborn T cells to respond during the very first stages of an infection and defend against a wide variety of unknown bacteria, parasites and viruses, which the adult T-cells cannot do. “We know that neonatal T cells don’t protect as well as adult T cells against repeat infections with the same pathogen. But neonatal T cells have an enhanced ability to protect the host against early stages of an initial infection,” Rudd said. “So, it is not possible to say adult T cells are better than neonatal T cells or neonatal T cells are better than adult T cells. They just have different functions.”

References: SCIENCE IMMUNOLOGY, Vol 9, Issue 92, DOI: 10.1126/sciimmunol.adf8776