The relationship between platelet sialic acid and platelet associated IgG (PA-IgG)

For an analysis of relationship between platelet sialic acid and platelet associated IgG (PA-IgG), PA-IgG and sialic acid level in both platelet and plasma were measured. PA-IgG was measured by immunfluorescent assay. This immunofluorescent assay is based on the treatment of platelets with neuraminidase. Sialic acid levels of platelets and plasma were measured by the thiobarbituric acid method.In patients with thrombocytopenia (ITP, acute leukemic patients who received platelet concentrates from random donors), the PA-IgG positive rates (% PA-IgG) in neuraminidase-treated and non-treated platelets were 37.0±4.18% and 7.9±2.33%, respectively. The results indicated that % PA-IgG was significantly elevated by neuraminidase treatment of platelets.Platelets from normal controls had a mean sialic acid of 0.72+0.30mg/108 platelets. Platelets from the patients had a mean sialic acid of 0.86+0.44mg/108 platelets. Sialic acid levels of platelets were significantly elevated in the patients. Sialic acid levels of plasma were elevated in the patients, but there was no correlation between platelet and plasma sialic acid in the patients.These findings suggest that the higher quality of sialic acid on the patient platelets might inhibit the detection of the PA-IgG.