There were significant losses of platelets during filtration, which could add to the costs of WBC reduction and lead to possible increases in donor exposures. Filtration failures still occurred, despite careful observation of the standard filtration procedures. The number of total WBCs in pooled platelets before filtration has been identified as an important factor in determining the success of WBC reduction.

SINCE exchange of iron with the external environment is very limited (Finch, 1959), body iron kinetics are largely concerned with the continuous redistribution of iron within the body. Thc reticulo-cndothelial system is an important participant in internal iron turnovcr. It is believed to removc haemoglobiii or non-viable erythrocytes from the circulation, proccss the iron from the hacm moiety and return iron to the plasma for transport to the marrow and subscqucnt incorporation into haemoglobin. The reticulo-eiidothelial cells also serve as a potential reservoir for storage of iron not used for other purposes. The present studies were undertaken to examine the way in which this system processes iron derived from iionviablc crythrocytcs. METHODSThe gcncral plan of these studies involved: (I) tagging of erythrocytes with radioiron or radiochromium ; (2) damaging these cells so that they would disappear rapidly from thc circulation with a minimum of intravascular haemolysis ; (3) administering the labelled cells to compatible rccipicnts under a variety of experimental conditions, and (4) measuring thc rate of removal of these non-viable cells from the circulation, their tissue localization and the subsequent release of radioiron from the reticulo-endothelial cells. Most of the investigations wcre done on normal human volunteers and on patients. In certain situations where this was not feasible, experimental animals wcre cmployed. '4. Hiiurrarr StudiesErythrocytes tagged with radioiron were prepared by admiiiisteriiig radioiron citrate in iiiultiple intravenous injections over a 6-day period to patients with polycythaemia Vera.The maximal total doses of 3 mc of 55Fe or 1.5 mc of 59Fe had no recognizable cffcct on thc marrow function of the donor. Tagged cells were obtained from these donors 2 or inorc wccks later. Untagged erythrocytes were obtained from normal or polycythaemic donors.All donors wcre screened for evidence of hepatitis by liver-function tests. Blood was shown to be Compatible by routinc tests bcfore transfusion and was examined by stained smear for bactcrial contamination. Blood was taken into citrate and rendered non-viable by storage a t 4 O C. for 24-28 days, unless otherwise spccified. Thcse non-viablc cclls wcre administered in amounts varying from 0.01 ml. to 1.5 ml. of erythrocytes per kg. body weight and coiitaiiicd from I to 25 wc of 59Fe, or from 5 to 3 0 1.1c of 55Fe. The normal human rccipients were young adult males with haeniatocrit values between 42 and 50 per cent and lcucocyte couiits betwccii 5,000 and 10,000 pcr cu. nim. Also studied were patients with pernicious anaemia in early rcmission, iron deficiency, infection, iron-storage disease and aplastic anaemia.

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