^99mTc-rCR2 binds to C3d⁺ RBC.

Sensitised sheep red blood cells were incubated with human C6 deficient serum to generate C3d deposition on RBC in the absence of cell lysis. ^99mTc-rCR2 , ^99mTc-C2A or K41E ^99mTc-rCR2 were added to 2.5×10⁷ C3d⁺ cells. The percentage radioactivity bound to C3d⁺ cells was determined by gamma counting the activity associated with the cell pellet as percentage of total activity added. Error bars represent the standard error of the mean of n = 5.