Gene sets GS1 to GS14 are extracted from publications reporting gene expression signatures associated with purified subsets of CD4⁺ T cells.^20–22  T_FHs are defined as CD4⁺CD57⁺CXCR5⁺ cells isolated from tonsils,^20–22  and Th1 and Th2 cells were obtained from cord blood cells cultured in appropriate polarizing conditions.^19,21  The 97 transcripts (GenBank accession numbers) found by Kim et al²⁰  to be differentially expressed in T_FHs (CD4⁺CXCR5⁺CD57⁺) versus other CD4⁺ T-cell subsets (naive CD4⁺CD45RA⁺, early memory CD4⁺CXCR5⁺CCR7⁺), and effector memory CD4⁺CCR7⁻) were mapped to 76 unique gene symbols represented on the Affymetrix U133plus2 GeneChip (57 overexpressed genes [GS1] and 19 down-regulated genes [GS6]). We used available gene symbols and/or accession numbers provided by Chtanova et al^21,22  to map the described genes to the U133plus2.0 GeneChip. GS2 represents the top 100 genes overexpressed in T_FHs according to Chtanova et al.²¹  The ranking of these genes was as follows: summing the individual fold change values between T_FHs and the other T-cell samples (the maximum fold change was used for redundant data); ordering the sums from highest to lowest fold change; and selecting the top 100 genes as the first 100 genes in this ordered gene list. GS3 and GS7 correspond to the complete list of overexpressed and underexpressed genes in T_FHs compared to other CD4⁺ T-cell subsets,^21,22  respectively. The union of GS1 (n = 55) and GS3 (n = 405) yielded 443 overexpressed genes (GS4) in T_FHs. The intersection of GS1 (n = 55) and GS3 (n = 405) yielded 16 common overexpressed genes in T_FHs (GS5). The union of GS6 (n = 19) and GS7 (n = 45) yielded 63 underexpressed genes (GS8) in T_FHs. In both studies by Rogge et al¹⁹  and Chtanova et al,²¹  the gene expression signature of the Th1 and Th2 subsets was defined by comapping each subset to the other one. Probe set identifiers provided by Rogge et al¹⁹  in the Table S1 were mapped to Entrez Gene identifiers using annotations provided by Affymetrix (NETAFFYX: http://www.affymetrix.com/analysis/index.affx), which were then used to map to U133plus2.0 probe sets yielding 138 genes (GS9) specifically overexpressed in Th1 cells and 50 genes (GS12) specifically overexpressed in Th2 cells. The genes specific to Th1 and Th2 described by Chtanova et al²¹  were mapped to the U133plus2.0 GeneChip, yielding, respectively, GS10 (29 genes) and GS13 (28 genes). The union of GS9 (n = 138) and GS10 (n = 29) yielded 159 overexpressed genes (GS11) in Th1 cells. The union of GS12 (n = 50) and GS13 (n = 28) yielded 73 overexpressed genes (GS14) in Th2 cells.