[ELISA for platelet-associated IgG, IgM, and C3, and their clinical application]

The platelet-associated IgG (PAIgG) has been reported to elevate in the patients with idiopathic thrombocytopenic purpura (ITP) and other autoimmune diseases. However, low PAIgG levels have been often recognized in thrombocytopenia. We speculated about the increasing of other platelet-associated proteins in those patients, and tried to determine platelet-associated IgM (PAIgM) and platelet-associated C3 (PAC3) using a high sensitive competitive micro-ELISA as well as PAIgG. Our results showed the specific elevation of PAIgM and PAC3 in thrombocytopenia as well as the PAIgG level (p less than 0.01). Further, the weak correlations among these levels were found (PAIgG/PAIgM: n = 7, correlation coefficient (r) = 0.55, PAIgG/PAC3: n = 73, r = 0.61, PAIgM/PAC3: n = 56, r = 0.39). We discussed on the possibility that the PAIgM and PAC3 also could be an indicator for the platelet injury and may cause the short platelet life span resulting thrombocytopenia as well as PAIgG.