Gene expression analysis performed in our study showed that factors expressed in the lungs of F2 mice segregated into two major groups: those not correlated with TB progression (iNOS, IL-12p40, IFN-γ, CCL5), and those associated with TB progression (IL-1β, IL-6, CCL3, CCL4, CXCL2, MMP-8, MMP-10, Figure 2 and data not shown). The gene discussed is CCL3; the disease is tuberculosis.