CD55 and CD59 Deficiency in Transplant Patient Populations: Possible Association With Paroxysmal Nocturnal Hemoglobinuria–Like Symptoms in Campath-Treated Patients

Campath-1H therapy is directed to CD52, a small mw protein that has a glycosylphosphatidylinositol (GPI) anchor, which has a conventional structure similar to other GPI anchors such as CD55 and CD59. Paroxysmal nocturnal hemoglobinuria (PNH) results when cells have a somatic defect in the synthesis of GPI anchors and lack CD55 and CD59, as well as CD52. Several patients treated with Campath developed PNH-like symptoms with hemolysis and thrombosis. These patients were followed after therapy by measurement of peripheral CD55 and CD59 levels and showed an increased number of cells deficient in the expression of these molecules. Thereafter we instituted a screening program for the presence of CD55/59 levels in all pretransplant patients. Our results show that 17.3% of all pretransplant samples contained abnormal (9.7% of samples) or slightly abnormal (7.6% of samples) levels of granulocytes deficient in CD55 or CD59. This high prevalence of CD55/59 deficiency in Campath-treated patients with PNH-like symptoms suggests that a lack of these molecules (including CD52) could predispose to a complication of this immunosuppressive therapy.

Treatment of aplastic anaemia with granulocyte-colony stimulating factor and risk of malignancy. Italian Aplastic Anaemia Study Group

Granulocyte-colony stimulating factor (G-CSF) is being increasingly used in healthy volunteers to harvest haemopoietic stem cells. A possible role of G-CSF in the development of clonal disorders or leukaemia has been suggested. We analysed 144 patients with aplastic anaemia treated with immunosuppression protocols with or without G-CSF, with normal cytogenetics at diagnosis or immediately after immunosuppression. Our findings indicated that the risk of developing myelodysplasia or leukaemia was similar in patients with aplastic anaemia on immunosuppressive treatment with or without G-CSF. Therefore, it seems unlikely that G-CSF causes leukaemia in healthy volunteers.

Sustained long-term hematologic recovery despite a marked quantitative defect in the stem cell compartment of patients with aplastic anemia after immunosuppressive therapy

Previously, we reported that patients with aplastic anemia (AA) have profoundly decreased numbers of hematopoietic progenitor and stem cells as measured in the long-term culture initiating cell (LTC-IC) assay (Blood 1996;88:1983-1991). We now present results of a long-term prospective study of LTC-IC numbers in peripheral blood (PB) and bone marrow (BM) of patients treated with antithymocyte globulin and cyclosporin A. Numbers of secondary colony forming cells (secondary CFC) in long-term bone marrow culture (LTBMC) were used to quantitate LTC-IC. BM (N = 35) and PB (N = 41) secondary CFC from both untreated severe AA patients and responders to immunosuppressive therapy who were sampled up to 6 years after initial treatment were compared. Normal controls showed 148 +/- 38 (N = 17) and 16 +/- 3 (N= 14) secondary CFC per 10(6) in BM and PB, respectively. In cross-sectional analysis, prior to therapy, AA patients showed 2.6 +/- 1 (mean +/- SD) secondary CFC/10(6) BM MNC; within the first year after initial treatment (N = 14), secondary CFC number rose modestly to 8.2 +/- 2.2/10(6) MNC, and further increased to 15.8 +/- 7 (N = 17) at 2 years and 16.2 +/- 7/10(6) MNC (N = 25) 3 years after treatment. There was no further improvement in the secondary CFC numbers at 4, 5, and > or =6 years (N = 37). Thus, while BM secondary CFC increased about 6-fold at 3 years post-therapy compared to presentation, they remained about only 10% of normal despite hematologic recovery. Similar data were obtained for PB, with approximately 4-fold increase in secondary CFC numbers within 2 years of therapy, to about 15% of normal values. We confirmed these observations in patients studied serially over a period of 4 years: initial secondary CFC were 2.35 +/- 1/10(6) BM MNC and 0.11 +/- 0.1/10(6) PB MNC improving to an average of 6 +/- 1. 2 (BM; N = 12) and 2.4 +/- 1/10(6) MNC (PB; N = 14). In many cases of partial recovery, PB counts improve but do not normalize. When we studied secondary CFC numbers only in patients who achieved complete normalization of PB counts (ANC >1,500/mm(3); platelets >10(5)/mm(3) and absolute reticulocytes >5 x 10(4)/mm(3)), BM secondary CFC were significantly higher than in patients with partial recovery; the PB secondary CFC number was modestly increased but remained below the normal values. Within the group of patients with complete recovery, there was no correlation between the secondary CFC and time after initial treatment. In addition, there also was no correlation between the secondary CFC number at presentation and the quality of hematopoietic recovery. Despite a limited expansion potential of a severely reduced stem cell pool, their numbers are sufficient to provide a long-term supply of mature blood cells. Am. J. Hematol. 65:123-131, 2000. Published 2000 Wiley-Liss, Inc.

Sustained long-term hematologic recovery despite a marked quantitative defect in the stem cell compartment of patients with aplastic anemia after immunosuppressive therapy

Previously, we reported that patients with aplastic anemia (AA) have profoundly decreased numbers of hematopoietic progenitor and stem cells as measured in the long-term culture initiating cell (LTC-IC) assay (Blood 1996;88:1983-1991). We now present results of a long-term prospective study of LTC-IC numbers in peripheral blood (PB) and bone marrow (BM) of patients treated with antithymocyte globulin and cyclosporin A. Numbers of secondary colony forming cells (secondary CFC) in long-term bone marrow culture (LTBMC) were used to quantitate LTC-IC. BM (N = 35) and PB (N = 41) secondary CFC from both untreated severe AA patients and responders to immunosuppressive therapy who were sampled up to 6 years after initial treatment were compared. Normal controls showed 148 +/- 38 (N = 17) and 16 +/- 3 (N= 14) secondary CFC per 10(6) in BM and PB, respectively. In cross-sectional analysis, prior to therapy, AA patients showed 2.6 +/- 1 (mean +/- SD) secondary CFC/10(6) BM MNC; within the first year after initial treatment (N = 14), secondary CFC number rose modestly to 8.2 +/- 2.2/10(6) MNC, and further increased to 15.8 +/- 7 (N = 17) at 2 years and 16.2 +/- 7/10(6) MNC (N = 25) 3 years after treatment. There was no further improvement in the secondary CFC numbers at 4, 5, and > or =6 years (N = 37). Thus, while BM secondary CFC increased about 6-fold at 3 years post-therapy compared to presentation, they remained about only 10% of normal despite hematologic recovery. Similar data were obtained for PB, with approximately 4-fold increase in secondary CFC numbers within 2 years of therapy, to about 15% of normal values. We confirmed these observations in patients studied serially over a period of 4 years: initial secondary CFC were 2.35 +/- 1/10(6) BM MNC and 0.11 +/- 0.1/10(6) PB MNC improving to an average of 6 +/- 1. 2 (BM; N = 12) and 2.4 +/- 1/10(6) MNC (PB; N = 14). In many cases of partial recovery, PB counts improve but do not normalize. When we studied secondary CFC numbers only in patients who achieved complete normalization of PB counts (ANC >1,500/mm(3); platelets >10(5)/mm(3) and absolute reticulocytes >5 x 10(4)/mm(3)), BM secondary CFC were significantly higher than in patients with partial recovery; the PB secondary CFC number was modestly increased but remained below the normal values. Within the group of patients with complete recovery, there was no correlation between the secondary CFC and time after initial treatment. In addition, there also was no correlation between the secondary CFC number at presentation and the quality of hematopoietic recovery. Despite a limited expansion potential of a severely reduced stem cell pool, their numbers are sufficient to provide a long-term supply of mature blood cells. Am. J. Hematol. 65:123-131, 2000. Published 2000 Wiley-Liss, Inc.

Production paroxysmal nocturnal hemoglobinuria-like red blood cells by tea

Normal human red cells incubated with saline extracts of tea develop paroxysmal nocturnal hemoglobinuria-like defects as demonstrated by positive acid and sucrose hemolysis tests. All of a variety of tea preparations tested provoked a sensitivity to complement-dependent hemolysis and, with one exception, a moderate decrease in red cell acetylcholinesterase activity. Complement-dependent hemolysis in teaincubated red cells was inhibited by antisera to C3 and C3 activator, but not by antisera to C4. This suggests that incubation with tea may alter the red cell membrane in a way that specifically potentiates the lytic effects of the alternate pathway of complement, but not the classic pathway. Leupeptin, a protease inhibitor, also prevented complement-dependent hemolysis of red cells incubated with tea. Although the clinical consequences of these observations are unknown, the study was initiated following a report of a young male who had developed an acute limited intravascular hemolytic episode following ingestion of large quantities of a herbal tea.

Two rare complications of chronic benzene poisoning: myeloid metaplasia and paroxysmal nocturnal hemoglobinuria. Report of two cases

Two patients, one with myeloid metaplasia and the other one with PNH, both due to chronic exposure to benzene are presented. The patient with PNH exhibited also marked monocytosis as a rare hematologic finding of chronic benzene exposure. The etiological relationship between myeloid metaplasia, PNH and chronic benzene exposure is discussed.