Ferritin secretion by human mononuclear cells: association with HLA phenotype.

A number of different observations indicate that cells of the immune system can participate in the prevention of potential tissue toxicity from iron accumulation and that, in turn, iron and iron binding proteins have important effects on immune responses. The current studies were undertaken to examine a specific aspect of the interaction of iron with human peripheral blood mononuclear cells. A modified hemolytic plaque-forming assay was used to measure ferritin secretion in vitro by phytohemagglutinin activated or nonactivated mononuclear cells in response to stimulation by ferric citrate. Cells from 55 unrelated healthy subjects collectively representing all well-defined HLA-A, B, C, and DR antigens were studied. There were large reproducible differences in the numbers of plaques formed by different individuals, and there was a statistically significant increase in the frequency of the HLA determinant A3 among the "low" responders. Ferritin secretion measured with an antibody specific for acidic ferritin also showed a distinction between A3 and non-A3 donors. In preliminary cell mixing studies, ferritin secretion by mononuclear cells was shown to require the presence of monocytes and to be influenced by the secretion characteristics of both the monocyte and the T-cell donor. These results may provide a clue to the mechanism of development of idiopathic hemochromatosis which is an HLA-A-linked autosomal recessive disease associated with the specific HLA antigen HLA-A3.