Changes in anti-TPO antibody levels, TPO concentrations,and platelet counts during cyA treatment.

Anti-TPO IgG antibodies were measured with a solid-phase radioimmunoassay. Briefly, microtiter plates were incubated with 4μg/mL of recombinant human TPO at 4°C overnight and washed. Test sera diluted at 1:10 in phosphate-buffered saline were added to the wells and incubated at 37°C for 1 hour. After washing, the wells were incubated with radioiodinated protein A at room temperature for 2 hours. Finally, the radioactivity bound to the wells was measured with a gamma counter. Data from the assay validation using rabbit polyclonal IgG antibodies against human TPO showed that the intra- and interassay coefficients of variation ranged from 6.3% to 10.3% and from 7.9% to 13.4%, respectively. Serum TPO levels were measured as described previously.7