Heavy chain ferritin (H-ferritin) is a component of the iron-binding protein, ferritin. We have previously shown that H-ferritin inhibits anti-CD3-stimulated lymphocyte proliferation and that this was due to increased production of interleukin-10 (IL-10). In the present study we have shown that induction of IL-10 production was due to effects of H-ferritin on adherent antigen-presenting cells (
IntroductionThe growth of melanoma, especially in its more advanced stages, can be associated with suppression of immune responses to the tumor and to other antigens. 1,2 Induction of anergy to melanoma antigens due to lack of costimulatory molecules or production of reactive oxygen metabolites is one possible mechanism for such changes. 3 In addition, a number of soluble factors produced by melanoma cells have been described that down-regulate immune responses via direct effects on lymphocytes or on antigen-presenting cells (APCs) in the vicinity of the tumor (reviewed by Hersey 4 ). Such factors include vascular endothelial growth factor, 5,6 interleukin-10 (IL-10), 7 and transforming growth factor- (TGF-). 8,9 We have recently reported that heavy chain ferritin (H-ferritin) appears to be another factor released by melanoma cells that may suppress immune responses by its ability to induce IL-10 production in lymphocytes. 10 Ferritin is a major tissue iron-binding protein 11 and in its native form has a molecular weight of approximately 500 kd. It is composed of 24 subunits consisting of acid/heavy (H) and basic/light (L) chains. 12,13 The genes encoding H-ferritin and light chain ferritin (L-ferritin) are found in different chromosomes and are transcriptionally independent. 14 The 24-subunit polymer may form isoferritins, which are either more acidic (H-rich) or more basic (L-rich) depending on the relative proportions of H and L chains. Liver and spleen ferritins are basic, because they are made up mainly of light chains and very few heavy chains. In contrast, heart, kidney, and placental ferritins are highly acidic, because they are composed mostly of heavy chains. 15 The ferritin found in cancer cells was found to consist mainly of heavy chains. 16,17 Marked variability was found in the ratios of H-to L-ferritin in supernatants from melanoma cultures. Some melanoma cells released predominantly H-ferritin, whereas others contained more equal proportions of H-and L-ferritin. 10 The immunosuppressive effects of the supernatants correlated with their content of Hferritin. These findings were consistent with previous reports that H-ferritin could suppress proliferation of T cells [18][19][20] and E rosette formation. 21 In our previous studies it was found that monoclonal antibodies (mAbs) against H-ferritin or against IL-10 could reverse the immunosuppressive effects. The latter was produced from lymphocytes exposed to H-ferritin and was associated with small decreases in IL-2 and IL-4 production. Interferon-␥ (IFN-gamma) production was also increased in lymphocytes exposed to H-ferritin. 10 In the present study we ha...