Defective T-lymphocyte E rosette (ER) function associated with viral hepatitis A and B may be due to mechanisms extrinsic or intrinsic to the target lymphocyte. The extrinsic defect is induced by an immunoregulatory plasma lipoprotein (RIF) and has the capacity to regenerate ER function in vitro. The intrinsic defect is refractory to regeneration and is not associated with RIF. Although both mechanisms occur with high frequency during the acute phase of viral hepatitis they tend to segregate in accordance with progression of hepatocellular injury at later stages of the disease. The extrinsic defect was observed in 7 out of 8 patients with longstanding chronic active hepatitis and in 10 out of 10 patients with unresolved hepatitis 12 wk after the onset of jaundice. In contrast, none of nine patients with resolved hepatitis had extrinsically defective ER function 12 wk after the onset of jaundice whereas eight of them displayed an intrinsic defect of ER function at that time. Among the various viral and liver diseases studied RIF appeared to be specific for hepatitis A and B viral infections. None of 64 sera from a variety of viral infections including Epstein-Barr virus cytomegalovirus mononucleosis with associated hepatitis nor 15 sera from patients with several chronic nonviral liver diseases were positive for RIF. RIF and its associated extrinsic defect in ER function therefore appear to correlate with a particular type of hepatocellular injury initiated by the hepatitis A and B viruses that may have a propensity for persistence and(or) progression to an aggressive form of chronic hepatitis.