On re-exposure to the same antigen, which change is characteristic of the secondary immune response?
1A slow rise in IgM without class switching
2No measurable change in antibody levels
3A rise limited to IgE antibodies
4A rapid rise in IgG with higher affinity✓ 정답
해설
Because memory cells already exist, the secondary response is faster and stronger, IgG predominates, and antibody affinity increases. The short lag phase and the higher peak titer compared with the primary response are the key points.