Expression of cell surface transferrin receptor and intracellular ferritin after in vitro stimulation of peripheral blood T lymphocytes.

Measurements of peripheral blood lymphocyte surface transferrin receptor using flow cytometry show that phytohaemagglutinin (PHA) stimulation causes a marked increase in both the number of cells bearing receptors and the absolute number of receptors. This increase is accompanied by the interleukin-2 receptor and there is a progressive increase of cells in the S phase of their cycle. Furthermore, ferritin synthesis in proliferating cells, as determined by immunoprecipitation techniques, increases significantly compared to non-stimulated cells. Intracellular concentrations of both spleen-type and heart-type ferritin are also increased with a preferentially high proportion of heart-type ferritin. These results suggest that expression of transferrin receptor and synthesis of ferritin is regulated by a complex mechanism. Cellular proliferative activity increases the expression of transferrin receptor and could modulate the biosynthesis of intracellular ferritin that is normally controlled by iron. These two processes do not appear to be linked.