Innate differences in immunity can be detected at birth, according to new research at Washington University School of Medicine in St. Louis. And babies with a better innate response to viruses have fewer respiratory illnesses in the first year of life.
"Viral respiratory infections are common during childhood," says first author Kaharu Sumino, MD, assistant professor of medicine. "Usually they are mild, but there's a wide range of responses - from regular cold symptoms to severe lung infections and even, in rare instances, death. We wanted to look at whether the innate immune response - the response to viruses that you're born with - has any effect on the risk of getting respiratory infections during the baby's first year."
Reporting in the May issue of the Journal of Allergy and Clinical Immunology, Sumino and her colleagues found that newborns with a diminished immune response to viruses experienced more respiratory infections in their first year of life than newborns whose immune response was more robust.
Using umbilical cord blood samples taken in the delivery room, the researchers measured a specific immune system response to viral infection known as interferon-gamma (IFN-gamma). IFN-gamma is released by some cells of the immune system when they encounter a virus. An important weapon in the immune system's arsenal, IFN-gamma helps fight viruses by stopping them from replicating.
The researchers studied cord blood samples from 82 babies in St. Louis enrolled in the Urban Environment and Childhood Asthma (URECA) trial. Eighty-five percent of the infants were African-American, and all lived in an area where at least 20 percent of the residents were below the poverty level. All had at least one parent with allergies, asthma or eczema, putting them at higher risk for these conditions themselves.
As reported by their caregivers, the babies averaged four colds in their first year with 88 percent of them suffering at least one cold. But the range varied widely with some caregivers reporting no colds and a few reporting as many as nine or 10.
To measure the innate immune response, the blood samples were taken at birth, before any exposure to the environment could influence the child's immunity. The researchers isolated monocytes, a specific type of white blood cell, from the babies' cord blood, and infected these cells with a common respiratory virus. They then measured the amount of IFN-gamma produced by the monocytes in response to the virus.
In general, babies whose monocytes responded to the virus by producing higher levels of IFN-gamma had fewer reported colds. Likewise, babies whose monocytes produced lower IFN-gamma levels had more reported colds.