A Fluorescent Microsphere Method for the Investigation of Erythrocyte Chimaerism after Allogeneic Bone Marrow Transplantation Using Antigenic Differences

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Abstract
A method for the investigation of erythrocyte chimaerism in patients after bone marrow transplantation (BMT) has been developed using fluorescent microspheres coated with anti-human IgG. Blood group antigens different in patient and donor were used as marker. The specificity and reliability of this method was evaluated measuring artificial mixtures of blood group positive and negative red cells. Red cell antigens tested were D, c, K, Fya, Fyb, Jka, Jkb, S and s. Mean linear regression lines for mixtures with percentages positive cells ranging from 0.01 to 1% and 1 to 100% were 0.91X-0.03 (r = 0.99) and 1.00X-0.05 (r = 0.99), respectively. The sensitivity level of the assay was one positive cell per 10,000 blood group negative cells. In negative control samples (n = 15) a mean percentage positive cells was found of 0.002 +/- 0.004 (SD). Intra- and inter-assay coefficients of variation were 4.9 and 5.3% for mixtures of 10%, and were 11.1 and 24.6% for mixtures of 0.1% blood group positive cells. It is concluded that the described method can be used both to establish the take of donor marrow in an early phase after transplantation and to investigate mixed erythrocyte chimaerism long after BMT.