Fig. 4. (A) IL-10 production in EBV-positive and -negative Akata and Mutu cell clones. After 3 days of culture of 10⁶ cells in 1 ml of RPMI with 10% FCS, the amount of IL-10 in the culture supernatant was measured with a high-sensitivity IL-10 human ELISA system (Amersham Pharmacia Biotech). (B) Time course of IL-10 production in EBV-positive and -negative Akata cells. (C) RT–PCR analysis of viral IL-10 expression in EBV-positive Akata and Mutu cell clones. EBV-positive Akata cells treated with anti-Ig antibody were used as a positive control for detection of viral IL-10.