Expression of the blood group I, i, H, and A1 antigens on erythrocyte membranes studied by immunofluorescence.

A double immunofluorescence technique was used to study the expression of I, i, H and A1 antigens on individual erythrocytes of neonates, adult controls and patients with various haematological disorders. I, i and H staining was heterogeneously distributed from cell to cell as was already demonstrated for A1 antigen. i staining occured in 41 to 64% of cord cells (11 to 32% were strongly fluorescent) but only in 0.2 to 2.3% of adult erythrocytes. I staining occurred in 54 to 97.5% of adult erythrocytes but only in 1 to 14% of those of cord blood. Patients' cells tended to mimic a foetal pattern of heterogeneity in that an increase of i stained cells occured associated with a decrease of A1 or H stained cells. It is suggested that the foetal-like red cells observed in patients with haematological disorders result from an expansion of a normal process of differentiation rather than clonal development of abnormal cells.