Shanghai Blood Center, Shanghai, China (People's Republic)
Background/Case Studies: A 35-year-old Chinese G3 P1 female, type B+, Jk(a-b-), with no history of blood transfusion or transplantation, was referred to the Shanghai Blood Center for exclusion of irregular antibodies other than anti-Jk3. Her husband is O+, Jk(a+b-), and the second pregnancy was terminated at 36 weeks, resulting in a stillbirth with unknown blood type. The maternal plasma showed heterogeneous agglutination with Jk(a+b+), Jk(a+b-), and Jk(a-b+) panel cells, and showed the same main side cross-matching result withsix O+, Jk(a-b-) donors,negative in saline and column agglutination media, while weakly positive in polybrene medium, and 2+ in polyethylene glycol (PEG) enhanced IAT. The Rh typing of the mother, her husband, and six donors are ccEE, CcEe, and CCee,respectively.
Study
Design/Methods: The laboratory conducted two two-step absorption-elution assays using RBCs with different RhCE and Kidd phenotype combinations to cross-verify and confirm the specificity of the complex antibodies in the maternal plasma. In the first assay, EEcc, Jk(a+b-) cells were reacted with the plasma, then the post-absorption supernatant was used to verify the specificity of the non-Kidd antibodies. At the same time, the elution fluid was reacted with Jk(a-b+) cells for a second elution to identify the specificity of the Kidd antibodies. In the second assay, CCee, Jk(a-b-) cells were used for the first absorption step with the plasma, and conversely, the elution fluid was used to identify non-Kidd antibodies, while the supernatant was used for the second step with Jk(a-b+) cells. In addition, the laboratory conducted relevant tests for HDN using the subsequently obtained cord blood from the newborn (39 weeks).
Results/Findings: The results showed that the maternal plasma contained anti-Jk3 and anti-Jka, with titers of both 1:4, accompanied with weak anti-Ce (detectable only by PEG enhanced IAT). The newborn is B+, ccDEE, with positive DAT (± for IgG & 2+ for C3d), while negative for IgM anti-Jka and anti-Jkb reagent. The local blood bank detected anti-Jka in the cord blood, whileelution study was inconclusive. Other newborn laboratory results showed a gradual decrease in Hb (201→153 g/L, reference value: 180-190 g/L) and an increase in bilirubin (I-Bil: 61.72→150.31 umol/L, reference value: 1.7-10.2 umol/L) within 5 days after birth. Conclusions: In this case study, two-step absorption-elution assay was used to confirm the presence of anti-Jk3, anti-Jka and anti-Ce in the plasma of Jk-null multiparous women, the extremely weak anti-Ce may be associated with maternal-infant Rh isotype. The cord blood detection of anti-Jka and DAT positive for C3d, along with the presence of low-titer Kidd antibodies in thematernal plasma suggest suspected HDN.The negative reaction of the newborn's RBCs with IgM anti-Jka may be due to epitope masking caused by antibody or complement sensitization on the cell surface.
