GAMMA-INTERFERON MODULATES HUMAN MONOCYTE MACROPHAGE TRANSFERRIN RECEPTOR EXPRESSION

  • 1 June 1988
    • journal article
    • research article
    • Vol. 71  (6) , 1590-1595
Abstract
Although circulating human monocytes do not express transferrin (Tf) receptors, cultured adherent blood cells display high-affinity Tf binding sites. In the present studies, effects of various cytokines and biologically active proteins on human monocyte/macrophage Tf receptors were investigated. After culture, Tf receptor expression by adherent blood cells was time dependent and plateaued by 7 days. The addition of interleukin-1 (IL-1), .alpha.-interferon (.alpha.-IFN), granulocyte/macrophage-colony stimulating factor (GM-CSF), or human IgG to macrophages cultured for 4 days did not alter Tf receptor expression. Fe-saturated, human Tf caused a significant, dose-dependent decrease in receptor expression. AT a dose of 100 U/ml, .gamma.-interferon (.gamma.-IFN) significantly increased Tf receptor expression by macrophages cultured for 4 (230% .+-. 51% of control) or 7 days (150% .+-. 22%). Scatchard analyses showed increased binding sites but no change in receptor affinity. Northern and slot blot analysis of cellular mRNA from macrophages cultured for 4 or 7 days and exposed to .gamma.-IFN showed a two- to fivefold increase in Tf receptor mRNA, but .ltoreq. 30% increase in .beta.-actin mRNA. Ferritin content of .gamma.-IFN-treated macrophages was 47% to 63% of control cells. Net uptake of 59Fe from Tf by .gamma.-IFN-treated cells was 10% to 17% of control, but uptake of radiolabeled Tf was comparable. When macrophages were labeled wtih 59Fe and then exposed to .gamma.-IFN, cell-associated Fe was reduced by 43%, indicating that .gamma.-IFN caused macrophage Fe release. .gamma.-IFN specifically modulates Tf receptor display by inducing Fe release and reducing cellular Fe content. Regulation of Tf receptor expression in macrophages is controlled by cellular Fe content and is thus similar to regulatory mechanisms in dividing cells.

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