Erythrocyte survival in normal mice and in mice with autoimmune haemolytic anaemia.

Erythrocyte survival has been studied in a strain of mice which develop autoimmune haemolytic anaemia in adult life (NZB/B1), and also in CBA and C57B1 mice, using one or both of two radioactive isotope labels, Cr and P. Erythrocyte survival is customarily expressed as the half-life but this is unsatisfactory for purposes of statistical comparison and we have used instead a parameter `κ' which represents the slope of the line obtained when: log(Counts per unit haemoglobin on day )/(Counts per unit haemoglobin on day 0) is plotted against time. Young NZB/B1 mice yield values of κ intermediate between those obtained in CBA and C57B1 mice, and may reasonably be judged to show normal erythrocyte survival. On the other hand, in older NZB/B1 mice which are strongly Coombs positive and show reticulocytosis and anaemia, erythrocyte survival is greatly shortened. The survival of erythrocytes transfused to NZB/B1 recipients from isogeneic donors was found to be similar to that of the recipient's own erythrocytes, irrespective of whether or not the donor was Coombs positive or showed other evidence of haemolytic activity. The values of κ obtained in NZB/B1 mice were essentially the same with both labels; in CBA mice, however, a significant difference was observed.