B- and T-cell responses to PCV vaccine. (A) Log-transformed plot of mean serum IgG antibody responses for each of the 4 PCV serotypes tested over the course of the study. (B) CD4⁺ T-cell responses to the CRM-197 carrier protein on the basis of proliferation assays with the use of CFSE dilution; percentage of CFSE^dim cells after CRM-197 stimulation at various time points for 49 total patients are shown. Black circles indicate nonresponders; red circles, responders. A responder is defined as a patient having at least a 3-fold increase of the enrollment measurement at ≥ 1 posttransplantation time points.