Homozygote BPSM1m/m animals had significantly higher levels of circulating TNF than BPSM1m/+ littermates, and their arthritis and heart disease was much more severe.3 In the lungs, lymphocyte foci were larger in size in BPSM1m/m animals than in BPSM1m/+ animals, but not more numerous (Figure 1a, see also Figure 3). Here, TNF is linked to arthritic joint disease.