CR1 and neoplasm: In our study, it is therefore likely that the apparent similar uptake-rates of Ad5wt and Ad-3∆-A20T in tumours were due to the lack of Ad5wt erythrocyte-binding since the ablation of CAR- and CR-1-binding, a “design feature” of the Ad-3∆-A20T could not be demonstrated in our murine model as such binding is obsolete in mice.