Asynchronous expression of granulocyte membrane receptors in megaloblastic anaemia

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Abstract
The expression of Fc(IgG) and C3b membrane receptors by granulocytes and their precursors was examined in 23 [human] cases of megaloblastic anemia which were graded I-III according to morphological severity. Fractionated bone marrow and peripheral blood granulocyte receptors were assessed by rosette formation with optimally sensitized ox erythrocytes and the results compared with those found in 14 normal marrows. Promyelocyte Fc and C3b receptor activities in megaloblastic anemia did not differ from normal while the number of Fc receptor positive myelocytes and later cells showed a significant increase (P < 0.05 in grade I, P < 0.01 in grades II and III) proportional to the severity of megaloblastosis. An increase in the number of C3b receptor positive granulocytes was seen in early megaloblastic anemias and, in contrast to Fc receptor expression, showed the highest receptor activities in the grade II cases. The most significant changes in receptor expression were seen at the metamyelocyte stage and appear to be related to the numbers of these cells found in the megaloblastic marrows. These alterations apparently are primarily related to asynchronous granulocyte maturation and the application of these findings to the study of granulocytic disorders is discussed.