Contrary to what was previously thought, newborn immune T cells
may have the ability to trigger an inflammatory response to
bacteria, according to a new study led by King's College London.
Although their immune system works very differently to that of
adults, babies may still be able to mount a strong immune
defense.
Our immune system is made up of several different types of
immune cells, including neutrophils which play an important role in
the frontline defense against infection, and lymphocytes: B cells
which produce antibodies, and T cells that target cells infected
with viruses and microbes.
Up to now, it was generally believed that babies have an
immature immune system that doesn't trigger the same inflammatory
response normally seen in adults. Although babies need to protect
themselves from the harmful pathogens they are exposed to from
birth, it was thought that their T cells were suppressed to some
extent to prevent inflammatory damage to the developing child.
Sceptical of this notion, the King's-led study set out to
characterise the properties of T cells, examining very small
samples of blood in twenty-eight highly premature babies, as they
developed over the first few weeks of life.
The team discovered that whilst T cells in newborn babies are
largely different to those in adults, it is not because they are
immunosuppressed; rather, they manufacture a potent anti-bacterial
molecule known as IL8 that has not previously been considered a
major product of T cells, and that activates neutrophils to attack
the body's foreign invaders.
Dr Deena Gibbons, of the Department of Immunobiology at King's
College London, said: "We found that babies have an in-built
anti-bacterial defense mechanism that works differently to adults,
but nevertheless may be effective in protecting them. This may also
be a mechanism by which the baby protects itself in the womb from
infections of the mother. The next stage of our work will be to
better understand the pathways that result in the immune cells of
newborns being so different to those in adults."
This T cell activity could become a target for future treatments
aimed at boosting the immune system of neonates in intensive care,
where infection is a major risk for morbidity and mortality.
Premature babies are also at serious risk of developing
inflammatory diseases such as necrotising enterocolitis (NEC),
where severe inflammation destroys tissues in the gut. NEC is the
most common gastrointestinal surgical emergency in preterm babies,
with mortality rates of around 15 to 30 per cent in the UK.
The paper, Interleukin-8 (CXCL8) production is a signatory T cell effector
function of human newborn infants, is published inNature Medicine.