Macrophage origin of Reed-Sternberg cells: an immunohistochemical study

In an immunohistochemical study of 26 biopsies from 24 patients with Hodgkin's disease a granular staining pattern for alpha-1-antitrypsin (α₁AT) and alpha-1-antichymotrypsin (α₁ACT) was seen in Reed-Sternberg (RS) cells and mononuclear Hodgkin's (H) cells in over half the cases. The pattern of staining for these antiproteases seen in RS and H cells has previously only been observed in normal and malignant cells of the monocyte/macrophage lineage within the lymphoreticular system. A faintly granular evenly distributed staining for IgG was found in viable RS and H cells. This staining was associated with a similar distribution of both light chains but not J chain, suggesting that the immunoglobulin had not been synthesised by these cells but had been taken up from the extracellular environment. It is suggested that this uptake is an active process occurring in viable RS and H cells, possibly via Fcγ receptors and further supports an origin from cells of the monocyte/macrophage lineage. IgA, IgD, albumin, fibrinogen, C1q, C4 and C3 were present in some cells, IgM was more rarely found and lysozyme was absent. The fact that cells staining for these serum proteins generally showed signs of degeneration and that the extent of staining correlated with the molecular weight, but not serum concentration, of the protein suggests that they are passively acquired by dead or dying cells and thus represent a separate phenomenon from IgG uptake. The function of IgG uptake and accumulation by RS cells and the α₁AT and α₁ACT markers may prove of use in identifying the macrophage subtype from which these cells are derived.