Splenic pulp, plasma cells and foamy histiocytes in immune thrombocytopenia: combined morphometric immunohistochemical and ultrastructural studies.

Spleens from 16 splenectomized patients with immune thrombocytopenia (ITP) were compared with 10 controls (accidental and incidental splenectomy, staging laparotomy). Fresh unfixed material was secured for smears and cryostat sections, and splenic tissue was fixed by perfusion for histomorphometric, immunohistochemical and ultrastructural examination. The volumes of white pulp, including germinal centres, red pulp, and trabeculae and vessels were estimated. The ratio plasma cells containing various Ig-classes/total nucleated cells and the ratio immature/mature plasma cells were determined and the occurrence and character of foamy cells examined. There were slightly increased absolute volumes of white pulp, red pulp and trabeculae + major vessels in ITP, but the differences were not statistically significant. There was a statistically significant raised number of IgG-, IgA- and IgM-containing plasma cells in the germinal centres in ITP. More IgG-containing cells seemed to be immature than in controls, but the difference was not statistically significant. Light microscopy showed foamy histiocytes in 7 of 16 cases, but electron microscopy showed them in all cases of ITP. Foamy histiocytes reacted with antithrombocyte serum.