With long, cold nights drawing in and people becoming more prone to sniffs and snuffles as winter tightens its icy grip, immune systems may have to work extra hard over the coming weeks in order to keep people fighting fit.
Now, a study from Oxford and Lund Universities has provided better understanding of the system that helps to protect us from illness, having gained further insight into how and when it is formed.
Previously, it was thought that the very first cells that kickstart the development of the immune system - referred to as immune-competent cells - originate from blood stem cells in the liver while the foetus is still developing.
However, this research has presented the idea that these particular cells could be formed much earlier in the embryo's yolk sac. This would mean that they come from a period before blood stem cells are even formed, which therefore contradicts the former theory.
A human embryo's yolk sac is formed around the fifth week of pregnancy.
According to established knowledge, the first blood stem cells are formed in the aorta region, from where they travel to the liver and go on to drive blood formulation during the foetal stage of gestation.
Once a baby is born, such processes move to the bone marrow, and the liver no longer produces these blood cells.
It is hoped that this new knowledge will help scientists and medical professionals to improve their knowledge of why and how children develop certain diseases, such as leukaemia, which in turn may help these to be treated.
"Knowledge of this is important because it helps us to understand how and when our immune system begins to form and what can go wrong in that process," commented postdoctoral fellow at Lund University Charlotta Boiers, adding that investigations would continue in order to better understand this biological process.