Comparative flow cytometric phenotypic analysis of blood tetC^NEG, tetC^INT, and tetC^HIGH PCs obtained 6 days after tet immunization. A representative experiment is presented in the top row (top series of dot plots) showing the expression of isotypic control, CD27, CD38, CD138, and HLA-DR, respectively, by tetC^NEG, tetC^INT, and tetC^HIGHCD19 CD38^HIGH cells. The bottom row summarizes the results observed in several donors. Values are expressed as the MFI of expression for each molecule in positive PCs. Results represent the mean plus or minus SEM (n = 6). *Statistically significant differences.