Iron binding proteins in selected human peripheral blood cell sets: immunofluorescence.

Selected populations of human peripheral blood T lymphocytes, B lymphocytes, monocytes and polymorphonuclear cells were examined for their intracellular content of lactoferrin transferrin and ferritin by an indirect immunofluorescence technique. Lactoferrin was found in polymorphs but not in lymphoid cells. Two different lactoferrin staining patterns were observed which we designated 'perinuclear', characterized by a ring of positive material round the nucleus, and cytoplasmic, in which most positive material was distributed in the cytoplasm. The former staining pattern was found in high density polymorphs the latter was associated with low density polymorphs occasionally found contaminating the peripheral blood mononuclear cell suspension. After incubation in vitro, the perinuclear pattern changed to cytoplasmic staining. Transferrin was found in T cells and polymorphs. In contrast, only a few transferrin containing cells were detected in the B cell and monocyte fractions. Following overnight incubation, a halo of positive material was found surrounding T cells stained for transferrin, suggesting that T cells released transferrin during incubation. Ferritin was also found in T cells and adherent cells. Following latex particle ingestion, the intensity of ferritin staining was markedly increased. Only a small proportion of lymphoid cells and monocytes stained for transferrin or ferritin in the total peripheral blood mononuclear cell suspension. The results indicate, therefore, that in response to manipulation procedures used routinely for the selection of human peripheral blood lymphoid cells, detectable amounts of transferrin and ferritin are present in T but not B cells. The fact that T cells are equipped with proteins known to participate in binding and storage of iron may constitute, at least in part, the basis for the contribution of these cells to the regulation of other major biological systems.