Effect of proinflammatory cytokines on PIGA- hematopoiesis.
OBJECTIVE
Blood cells from patients with paroxysmal nocturnal hemoglobinuria lack glycosyl phosphatidylinositol (GPI)-linked proteins, due to a somatic mutation in the X-linked PIGA gene. It is believed that clonal expansion of PIGA- blood cells is due to a survival advantage in the hostile marrow environment of aplastic anemia. Here we investigated the effects of inhibitory cytokines in mice genetically engineered to have blood cells deficient in GPI-linked proteins.


METHODS
The effect of inhibitory cytokines (tumor necrosis factor-alpha [TNF-alpha], interferon-gamma [IFN-gamma], macrophage inflammatory protein-1 alpha [MIP-1alpha], and transforming growth factor-beta1 [TGF-beta1]) was investigated, using clonogenic assays, competitive repopulation, and in vivo induction of proinflammatory cytokines by double-stranded RNA. The expression of Fas on progenitor cells and its up-regulation by inhibitory cytokines were analyzed by flow cytometry.


RESULTS
TNF-alpha, IFN-gamma, MIP-1alpha, and TGF-beta1 suppressed colony formation in a dose-dependent fashion that was similar for PIGA+ and PIGA- blood bone marrow cells. Competitive repopulation of bone marrow cells cultured in IFN-gamma and TNF-alpha resulted in a comparable ability of PIGA+ and PIGA- hematopoietic stem cells to reconstitute hematopoiesis. Fas expression was minimal on PIGA+ and PIGA- progenitor cells and was up-regulated to the same extent in response to IFN-gamma and TNF-alpha as assessed by Fas antibody-mediated apoptosis. Similarly, in vivo induction of proinflammatory cytokines by double-stranded RNA had no effect on the proportion of circulating PIGA- blood cells.


CONCLUSIONS
These results indicate that PIGA+ and PIGA- hematopoietic progenitor cells respond similarly to inhibitory cytokines, suggesting that other factors are responsible for the clonal expansion of paroxysmal nocturnal hemoglobinuria cells.
Kulkarni
Shashikant
S
Department of Internal Medicine, Division of Hematology, Washington University School of Medicine, St. Louis, Mo. 63110, USA.
Bessler
Monica
M
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D019070:Cell Lineage / Q000187:drug effects / Q000235:genetics; D054405:Chemokine CCL3; D054407:Chemokine CCL4; D016207:Cytokines / Q000494:pharmacology*; D006410:Hematopoiesis / Q000187:drug effects* / Q000235:genetics*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D019402:Macrophage Inflammatory Proteins / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D054405:Chemokine CCL3; D054407:Chemokine CCL4; D016207:Cytokines; D019402:Macrophage Inflammatory Proteins; D008565:Membrane Proteins; C508960:TGFB1 protein, human; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; C080086:phosphatidylinositol glycan-class A protein; D007371:Interferon-gamma