Atypical hemolytic uremic syndrome (aHUS) is a disorder of the microvasculature with hemolytic anemia, thrombocytopenia and acute kidney injury. The pathogenesis of aHUS involves the uncontrolled activation of the alternative complement pathway [
1‐
5]. Nowadays, aHUS is successfully treated with eculizumab [
3‐
7]. Eculizumab is a humanized, chimeric IgG2/4 kappa antibody, which binds human complement C5 and blocks C5a generation and complement-mediated cell lysis via membrane-attack-complex [
6]. However, it is not known whether the administration of eculizumab in pregnant patients with end-stage renal disease due to aHUS may cause reduced membrane-attack-complex formation also in the fetal circulation. The objective of the present study was to alert clinicians to the effect of therapeutic antibodies in newborns.
For this report we measured the deposition of complement C3 and C9 in the mother’s blood, in index newborn’s umbilical cord vein blood (obtained after delivery, i.e., 2 h after the last eculizumab infusion), and in blood 3 weeks after birth we measured deposition of complement C3 and C9 using the Palarasah-Nielsen-ELISA as previously described [
8,
9]. The sensitive and specific Palarasah-Nielsen-ELISA determines the capacities of three complement pathways using wells pre-coated with immune complexes, lipopolysaccharides, or mannan, to activate classical, alternative, and lectin pathway, respectively [
9]. The deposition of C3 was measured using monoclonal anti-human C3, clone C3 F1–8, which identifies C3, C3b, iC3b and C3c; and deposition of C9 was measured using anti-human C9 (Bioporto A/S, Gentofte, Denmark), which reacts with the membrane-attack-complex [
9]. The advantages of the Palarasah-Nielsen-ELISA had been described [
9]. Briefly, CH50 and AH50 methods are not based on ELISA principle but based on the spectrophotometric measurements of the degree of cell lysis following addition of antibody-sensitized sheep erythrocytes and sheep erythrocytes in solution, respectively. The protocol for the CH50 and AH50 methods is laborious, difficult to standardize, and it is well established that the ELISA methodology is more sensitive compared to these older techniques. Further, and in contrast to the CH50 and AH50 methods, Palarasah-Nielsen-ELISA is able to distinguish complement capacity between C3- and C9 (membrane-attack-complex) -level.