How does transferrin slow the growth of bacteria in the body?

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Immune stimulation by activated helper T cells — immune system Stimulation of immune response by activated helper T cells. Activated by complex interaction with molecules on the surface of a macrophage or some other antigen-presenting cell, a helper T cell proliferates into two general subtypes, T_H1 and T_H2. These in turn stimulate the complex pathways of the cell-mediated immune response and the humoral immune response, respectively.

Transferrin is a blood protein that primarily functions to transport iron through the bloodstream to cells that require the mineral for growth.12

While its role is not specifically designed for immune defense, it provides an incidental protective effect against infection. Bacteria, much like human cells, require free iron to survive and proliferate. By binding to iron molecules in the bloodstream, transferrin effectively sequesters the mineral, making it unavailable to invading microbes. This process limits the amount of iron accessible to bacteria, thereby stemming their growth and helping to repel potential infections.2