To study the pathogenesis of multicentric Castleman's disease (MCD), IL-6 producing cells and immune function were investigated in four MCD patients. The expression of IL-6 mRNA in one MCD lymph node was analysed by in situ hybridization. IL-6 mRNA expressing cells were scattered in the interfollicular areas and did not resemble plasma cells. Spontaneous IL-6 production was detected in the culture supernatants of peripheral blood mononuclear cells (PBMNC) from four patients. The IL-6 producing cells among the PBMNC were found to be monocytes by both in situ hybridization and immunohistochemistry. We evaluated immune function in four MCD patients. These studies show: (1) a negative PPD skin test in 3/4 patients, (2) decreased IL-2 production in 3/4 patients, (3) decreased T cell colony formation in 3/4 patients, (4) decreased NK activity and NK cell number in 2/4 patients, (5) increased soluble IL-2 receptor in 4/4 patients, and (6) decreased CD4/CD8 ratio in 3/4 patients. These results show that MCD resembles, in several ways, acquired immunodeficiency syndrome (AIDS).

Background. To the authors' knowledge, there have been no reports describing a case of malignant paraganglioma that produces both adrenocorticotropic hormone (ACTH) and interleukin‐6 (IL‐6). Methods. The clinical course and pathophysiology of a patient with Cushing's syndrome induced by ectopic ACTH syndrome caused by a cervical malignant paraganglioma with elevated plasma levels of IL‐6 was investigated. Results. Ultrasonography, computed tomography, and magnetic resonance imaging of the neck revealed the presence of a tumor around the area from which the blood sample that showed the highest levels of ACTH and IL‐6 was obtained by selective catheterization. Immunohistochemical staining of the removed tissue demonstrated the presence of ACTH and IL‐6 proteins in the tumor cells. Reverse transcriptase‐polymerase chain reaction also revealed the existence of IL‐6 mRNA in those cells. Conclusion. The malignant paraganglioma of ectopic ACTH syndrome may produce IL‐6. The present investigation provides new observations concerning ectopic ACTH syndrome.

Erythroid cells in the marrow express CD71, transferrin receptor, and reticulocytes released from the marrow lose their expression during maturation. The immature reticulocyte fraction, the proportion of reticulocytes with the highest content of RNA, has been determined by hematology analysis. In the present study, we examined CD71 expression on immature reticulocytes by flow cytometry (FCM) in paroxysmal nocturnal hemoglobinuria (PNH) patients with reticulocytosis. We modified 'reticulocyte-gated FCM' to multi-color FCM, i.e. RNA/CD71, RNA-CD59 or CD59/CD71/CD45. In PNH, in addition to the increased number of immature reticulocytes (%CD71-positive), a more immature phenotype in regard to both CD71 intensity and RNA content levels was demonstrated. In seven PNH patients studied, %CD71-positive reticulocytes were significantly increased at 32.2 +/- 11.9% (n = 10, normal 10.4 +/- 3.5%, P = 0.002). RNA content levels (assessed by mean fluorescence index, MFI) in CD71-positive reticulocytes were significantly increased at 812.0 +/- 215.2 MFI in PNH (n = 10, normal 508 +/- 86.1 MFI, P = 0.002). These data indicate that stimulated erythropoietic conditions induce the release of more immature reticulocytes to the peripheral blood than ordinary erythropoietic conditions. CD71 intensity on immature reticulocytes was well correlated with their RNA content levels, indicating the usefulness of CD71 as an immature reticulocyte marker.

We have established a new nonlymphoid leukemic cell ine from a patient with myelodysplastic syndrome (MDS), which progressed to overt leukemia. The parental cell line and a subline derived from this line have absolute dependency on several cytokines for their long-term survival and growth. The parental line designated F-36P requires granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) for continuous growth, while a subline designated F-36E can be maintained in the presence of erythropoietin (Epo) alone. When these cytokines are depleted, both the parental and the subline cells die within several days, even in medium supplemented with fetal calf serum (FCS). F-36E, maintained in the presence of Epo, constitutively synthesizes hemoglobin at a significant level. F-36P, which is usually maintained in the presence of GM-CSF or IL-3, can be induced to synthesize hemoglobin when GM-CSF or IL-3 is substituted by Epo. The surface marker profile shows that the F-36P cells are positive for the leukocyte common antigen (CD45) and some common multilineage markers such as CD13, CD33, and CD34, and negative for T- and B-cell antigens and mature myelomonocytic antigens. However, some monoclonal antibodies recognizing erythroid and platelet glycoproteins react with these cells. Thus, this cell line has a multilineage phenotype, suggesting that the transformation event occurred in a multipotent stem cell. It is also evident that the F-36 cells can be induced to differentiate into the erythroid lineage in the presence of Epo. This, to our knowledge, is the first description of a human leukemic cell line that can be stimulated to synthesize hemoglobin by Epo.