To understand how these proteins are produced, the researchers turned to laboratory experiments. They generated human immune cells called macrophages — aggressive frontline defenders of the immune system — and exposed them to mRNA vaccines in a controlled dish setting. The macrophages responded by releasing a variety of cytokines, with CXCL10 produced in particularly notable quantities.
When a second type of immune cell — T cells, which serve as roving sentinels capable of recognizing specific threats and amplifying immune responses — was introduced to the dish, or even when T cells were simply placed in the fluid in which vaccine-treated macrophages had been bathed, IFN-gamma output increased dramatically. T cells exposed to the vaccine alone, without the macrophage-conditioned environment, produced only ordinary amounts of IFN-gamma. This finding established a clear sequence: macrophages are the primary source of CXCL10, and T cells are the primary source of IFN-gamma, with the latter depending on signals from the former.
