Inhibition of the plasma-dependent enhancement of CVB-induced IFN-α production by PBMC by preincubating plasma with VP4 (1 μg/ml). Plasma samples were obtained from 20 healthy subjects (a) and 20 IDDM patients (b). The procedure is described in the legend to Fig. 2. Means and standard deviations are presented. In the presence of VP4CVB3 protein, the results were 219 ± 123 IU/ml versus 29 ± 20 IU/ml (P < 0.001, n = 20) for healthy subjects and 409 ± 212 IU/ml versus 32 ± 25 IU/ml (P < 0.001, n = 20) for IDDM patients. In the presence of VP4CVB4 protein, the results were 96 ± 44 IU/ml versus 21 ± 13 IU/ml (P < 0.001, n = 20) for healthy subjects and 276 ± 197 IU/ml versus 38 ± 32 IU/ml (P < 0.001, n = 20) for IDDM patients.