How infants' immune system forgets to kill bacteria

Know why does your infant get infections every now and then? It has nothing to do with weak immunity but his/her immune system may have forgotten to act on time.

Forgetful immune systems leave infants particularly prone to infections, according to a study.

"Infants' immune systems actually respond to infection with more speed and strength than adults but the immunities they create fail to last," researchers from Cornell University said.

The perfect vaccine would be a single dose given at birth that generates long-lasting immunity.

"No such vaccine exists because we have not understood why infants rapidly lose immunities. Our finding could change the way we immunise infants and ultimately lead to more effective ways of enhancing immunity in early life," explained immunologist Brian Rudd from Cornell University's college of veterinary medicine.

Immunity against most microbes depends on forming "memory T cells" that remember specific pathogens and can rapidly respond to future infections.

Adults almost always generate large numbers of effective memory T cells during infection, around 10 percent of which stay in a long-lived memory pool to rapidly respond next time.

The team found that newborn T cells generated in response to infection met dramatically different fates.

When faced with the same pathogen, newborn immune systems made T cells that responded more rapidly to infection than adult cells, but quickly became terminally differentiated, never making it into the memory pool.

"So the immune system is forced to start the learning process over again when infected by the same pathogen later in life," Rudd said.

The research was published in the Journal of Immunology.