Expression of dimeric tumour necrosis factor receptor II (dTNFR) from pGTTMIK and gene therapy application in the collagen-induced arthritis (CIA) model. (a) Cos 7 cells were transiently transfected with 2 μg of pGTTMIK by the calcium phosphate method. Expression of dTNFR was induced for 24 or 48 hours with doxycycline (Dox) (1 μg/ml). Values are the mean of triplicate transfections, and induction values above the black bars allow for the endogenous production of TNFR II from non-transfected (NT) cells indicated by the dotted line. (b) Inhibition of CIA in mice treated with pGTTMIK and administered Dox. Progression of CIA both in terms of clinical score (I) and hind paw swelling (II) was inhibited by delivery of pGTTMIK (50 μg) intramuscularly with electroporation on day 28 after immunisation in mice with early disease (clinical score of less than 4). Inhibition was evident in those mice that received Dox in sweetened drinking water. Values are the mean, and vertical lines represent the standard error of the mean. Significant difference of p < 0.05 and p < 0.02 between the GTTMIK groups given Dox-containing and Dox-free sweetened drinking water are indicated by * and **, respectively.