A plasma inhibition study was performed on a patient whose serum sample reacted +/- on all panel cells at AHG. Three sets of A, B, C tubes were set up according to the following scheme: Tube A had 2 drops of patient serum and 1 drop of Ch(a+) Rg(a-) plasma.
Tube B had 2 drops of patient serum and 1 drop of Ch(a-) Rg(a+) plasma.
Tube C had 2 drops of patient serum and 1 drop of Ch(a+) Rg(a+) plasma.
Screening cells were added in triplicate and incubated for 60 minutes at 37°C. The antiglobulin test was performed. All three A tubes reacted at 2+, and the B and C tubes were negative. What antibody is indicated?