特発性血小板減少性紫斑病(ITP)と網内系

The spleens removed from 134 patients with chronic idiopathic thrombocytopenic purpura (ITP) treated in the 17 institutes in Japan were utilized in this study; the fresh surgical materials obtained in 18 of these cases were studied also by electron microscopy and immunohistochemistry. In ordinary HE sections, foamy macrophages were demonstrated in 55% of the 11 spleens from the patients without improvement after splenectomy, while the cells were found in only 25% of the 43 patients who revealed improved platelet counts after surgery. The foamy cells reacted strongly with a monoclonal antibody FU7 that was generated by using cultured malignant fibrous histiocytoma as an immunogen. When stained wite FU 7, there was a remarkable increase in the number of the recognizable foamy cells: 100% of the ITP spleens, and even 67% of the control spleens contained some positive cells. As to the subsets of T lymphocytes, the periarterial Iymphoid sheaths were rich in helper/inducer cells that outnumbered suppressor/cytotoxic cells. By electron microscopy, the ITP spleens showed pronounced phagocytosis of platelets by macrophages in the medullary cords and marginal zones; foamy macrophages were filled with numerous myelin figures and residual bodies probably deriving from incompletely digested platelet membrane. A mild increase of IgG-positive lymphoid cells and plasma cells in these regions, together with hyperplastic lymph follicles with prominent germinal centers in some cases, may represent the activated state of the B lymphocyte system in ITP. The follicles were generally atrophic and devoid of germinal centeres in the cases treated with prolonged steroid therapy.