These results might help to explain the differences in the severity of arthritis of BALB/c and ZAP-70+/− mice: when apoptosis decreased, activated T cells persisted in BALB/c mice, which kept the inflammation active and contributed to the more pronounced tissue injury, whereas in the partial absence of ZAP-70 the apoptotic processes remained close to non-arthritic controls (Figure 4 and Figure 5). This evidence concerns the gene ZAP70 and arthritic joint disease.