RELATIONSHIP BETWEEN SERUM UNCONJUGATED BILIRUBIN LEVELS AND THE AUTOFLUORESCENCE OF WHITE BLOOD-CELLS IN NEONATAL JAUNDICE

In this study, using flow cytometry, we investigated the auto-fluoresc ence emitted by lymphocytes, monocytes and neutrophils exposed to diff erent unconjugated bilirubin concentrations and investigated the relat ionship between these parameters. Different unconjugated bilirubin con centrations were prepared from a newborn serum with an unconjugated bi lirubin concentration of 800 mu mol/l. The same concentrations of unco njugated bilirubin have been prepared from pure bilirubin. 10 mu l of cord blood were incubated at room temperature for 15 min with 90-mu l solutions with different bilirubin concentrations prepared from both s erum and pure bilirubin. After incubation, cells were washed three tim es with PBS, erythrocytes were lysed by lysing buffer and run through flow cytometry immediately. Autofluorescence was measured by recording mean fluorescence channels for lymphocytes, monocytes and neutrophils . There was a good correlation between serum concentrations of unconju gated bilirubin that cells were exposed to and the autofluorescence in tensity of neutrophils 0.904, p < 0.005), monocytes (r = 0.759, p < 0. 05) and lymphocytes (r = 0.766, p < 0.01). Results obtained with pure bilirubin were also similar. Autofluorescence emitted by lymphocytes w as lower than that of monocytes (p < 0.01) or neutrophils (p < 0.0005) .