Suppose a researcher calculates the dissociation constant of the binding between two immunoglobulin G (IgG) antibodies, IgG-1 and IgG-2, and several antigens. He calculates the dissociation constant (K) of each IgG and antigen based on what concentration of the antigen causes half-maximal saturation of the IgG molecules. The Kd value reveals the affinity between the IgG molecules and the antigens. He needs to determine which antigen specifically binds IgG-1 or IgG-2 based on Kd.

Antigen Kd
A 9.1 x 10-5
B 3.2 x 10-11
C 2.7 x 10-6

IgG-1 binantigenta Kd (M)
A 4.0 x 10-10
B 7.4 x 10-10
C 1.8 X 10-11

Classify each antibody-antigen pair based on whether the IgG binds the antigen with high or low binding affinity.