Influence of 129 genetic background carryover on arthritis severity in ST2 KO mice. (A) Schematic representation of markers screened on chromosome 1, cM 0-32. (B) Heterogeneity of genetic background in ST2 KO mice upstream of the ST2 locus on chromosome 1, as assessed by size differences in markers D1Mit3 and D1Mit211, in the ST2 KO (n = 10, lanes 1 to 10) mice used for the arthritis experiment shown in Figure 1. M, size ladder; B6, C57BL/6 control DNA; 129, 129SvPas control DNA; F1, B6x129F1 hybrid control DNA; bp, base pairs. (C) Correlation of D1Mit211 (left panel), D6Mit159 (middle panel) and D15Mit193 (right panel) genotypes (B6, hybrid or 129) with maximal clinical arthritis severity scores in the ST2 KO mice (n = 20) used for the arthritis experiments shown in Figure 1 and 3. Absolute values for arthritis severity scores were corrected for overall mean maximal severity in each experiment. KO, knockout.