Limiting dilution analysis of autoreactive T cells in patients affected by hydatid disease.

We evaluated the peripheral autoreactive response in patients with Echinococcus granulosus compared with healthy individuals. A limiting dilution analysis (LDA) was performed to estimate frequency of auto-reactive T cells and to detect the complex mechanism that often underlies the autoreactive response. Different LDA curves were seen in healthy controls and patients. The control group provided a straight line passing through the origin ('single hit' kinetics), indicating that only peripheral autoreactive T cells are limiting. On the other hand, autoreactive T cell titration in hydatid patients did not follow 'single hit' kinetics, suggesting that two or more cell types are titrated. More interestingly, we observed a very high frequency of autoreactive T cells in hydatid patients (1/1,000 to 1/2,500) compared with healthy controls (1/5,000 to 1/35,000). These data suggest that chronic infection may provide adequate stimuli for the induction of autoimmune disorders and increase in autoreactive T cells.