Antibody dependent cell mediated cytotoxicity and erythrophagocytosis assays in Rh haemolytic disease of the newborn.

OBJECTIVE

To evaluate the role of antibody dependent cell mediated cytotoxicity (ADCC) and erythrophagocytosis in comparison to IgG subtypes and concentration of anti-D in haemolytic disease of the newborn (HDN).

DESIGN, SETTING AND PATIENTS: One hundred Rh (D) immunised women attending an antenatal clinic of Nowrosjee Wadia Maternity Hospital at 32 to 34 weeks of gestation. Results of 90 women having Rh (D) positive infants were correlated with severity based on outcome of pregnancy, cord blood Hb and treatment given to infant.

MEASUREMENTS

Immunoradiometric assay (IRMA) was used for anti-D quantitation. In ADCC assay 51Cr release in the culture supernatant was measured, and in the phagocytosis assay lytic activity was measured on spectrophotometer. Cord blood monocytes were used as effector cells in both the assays.

RESULTS

Good correlation (P < 0.01) was observed between ADCC vs IRMA and ADCC vs phagocytosis. ADCC% specific lysis was significantly higher and still-birth rate was increased when mothers had IgG1 + IgG3 type of anti-D. Though all variables showed significant correlation (P < 0.01) with severity, ADCC assay was the most predictive. Cord blood haemoglobin showed a significant inverse correlation with ADCC and phagocytosis assays.

CONCLUSION

In the absence of a cordocentesis facility severity of Rh HDN could be reliably judged by ADCC assay. If an isotope laboratory is not available, then instead of ADCC, phagocytosis assay may be employed.