Replication of Mycobacterium bovis (BCG) and splenomegaly response in different crosses. Informative F1 and F2 crosses were derived from mouse strains BXH-2, C57BL/6J (B6, panel B), C3H/HeJ (C3, panel C), BALB/cJ (BA, panel D), and A/J (A, panel E), in the combinations indicated at the top of each graph. (BALB/cJ × BXH-2) F2 animals were genotyped with a total of 193 polymorphic dinucleotide repeat markers providing an average coverage of 10 cM along each chromosome. For individual F2 crosses, mice were further separated according to homozygosity or heterozygosity for either mutant (Nramp1^D169, D) or wild-type (Nramp1^G169, G) alleles at Nramp1. At the time they were killed, spleen weight was determined and used to calculate the spleen index, as described in “Materials and methods.” Dots represent individual mice, and means for each group are shown as lines on the graphs.