Hierarchical clusterization comparing the 77 genes expressed differently at significant levels in spleen cells of naive and proteoglycan-immunized (not-yet-arthritic) mice of BALB/cJ and BALB/cByJ colonies (n = 3 of each, four-group cross-comparison: naïve BALB/cJ versus immunized BALB/cJ, naïve BALB/cByJ versus immunized BALB/cByJ, naïve BALB/cJ versus naïve BALB/cByJ, and immunized BALB/cJ versus immunized BALB/cByJ). Color code indicates the normalized intensity expression values (with baseline transformation) on a logarithmic scale. Twenty-three genes showing over twofold differences in any of the four comparisons are labeled with asterisks. Whenever a gene name was not identified (n = 14), the original probe set ID (number_at), the Riken ID (numberRik), or the expressed sequence tag clone number is used. Those genes that showed significant differences only in response to immunization (n = 8) are labeled with the '†' symbol. Original data files are available via Gene Expression Omnibus (accession number [GEO:GSE13730] and National Center for Biotechnology Information tracking system number 15549466).