High survival of frozen cells irradiated with gamma radiation.

Cell storage in liquid nitrogen (LN) offers the most secure method of cell preservation even if cryopreserved cells are exposed to natural background of ionising radiation (IR). A lot of experiments have demonstrated that IR can induce damages in living cells, but only a little information regarding the response of cryopreserved cells is available. To investigate the effect of IR on frozen and unfrozen cells, peripheral blood mononuclear cells were directly irradiated at room temperature, then immediately frozen, or frozen and then irradiated in LN with different doses of gamma rays. After thawing, cells were incubated and death fraction was evaluated at different time points. Interestingly, the percentages of dead cells induced by IR gradually increased with both dose radiation and incubation time and were significantly lower for cells irradiated at -196°C than those irradiated at room temperature.

The role of oxidant injury in the pathophysiology of human thalassemias.

The anemia in beta-thalassemia major is caused by a combination of hemolysis and ineffective erythropoiesis, with the latter being more important. Studies of the underlying cause of the hemolysis have indicated that oxidant injury to circulating red blood cells (RBCs) was of critical importance, with evidence of oxidant damage to RBC membrane proteins 4.1 and band 3. Therefore, it seemed reasonable that oxidant damage to thalassemic erythroid precursors would cause their accelerated apoptosis and ineffective erythropoiesis. However, direct analysis showed that the apoptotic programs turned on in thalassemics were not those triggered by oxidative damage but were dependent on activation of FAS/FAS-Ligand interaction. Thus, destruction of thalassemic erythroid precursors may involve different mechanisms from those that cause RBC hemolysis.

Enhanced macrophagic attack on beta-thalassemia major erythroid precursors.

BACKGROUND AND OBJECTIVES: In beta-thalassemia major (Cooley's anemia), ferrokinetic studies show that 60-80% of erythroid precursors die in the marrow or extramedullary sites. However, study of marrow aspirates does not reveal huge numbers of dead and dying erythroid precursors. We explored this apparent discrepancy with the hypothesis that enhanced phagocytosis of thalassemic erythroid precursors was a likely explanation. Prior studies had reported on an increase in thalassemic marrow macrophages and their enhanced state of activation. Therefore this study explored the characteristics of thalassemic erythroid precursors which might lead to enhanced susceptibility to phagocytosis. We have shown that enhanced erythroid apoptosis parallels the extent of ineffective erythropoeisis in thalassemic patients, and apoptotic cells are rapidly phagocytosed. Thus, increased apoptosis and perhaps other features of thalassemic erythroid precursors might be the cause of their enhanced phagocytic removal. DESIGN AND METHODS: Erythroid precursors were isolated from normal and beta-thalassemia major marrow, and incubated with uniform cultures of murine macrophages. The extent of phagocytosis was measured and then specific inhibitors were added to identify some of the messages effete erythroid precursors use to signal their condition to macrophages. RESULTS: Beta-thalassemia major erythroid precursors are phagocytosed twice as effectively as normal erythroid precursors. INTERPRETATION AND CONCLUSIONS: Experiments using inhibitors of phagocytosis showed that enhanced apoptosis is certainly responsible for part of the increased phagocytosis of thalassemic erythroid precursors. Interestingly, normal erythroid precursors are also subject to phagocytosis by qualitatively similar mechanisms.