Exogenous hepatitis B surface antigen particles processed by dendritic cells or macrophages prime murine MHC class I-restricted cytotoxic T lymphocytes in vivo

Injection of low doses of particulate hepatitis B surface Ag (HBsAg) into H-2(d) mice without adjuvants primes an L(d)-restricted, S_28-29-specific T cell response. This study indicates that dendritic cells (DC) and macrophages (Mφ) both serve as APCs that support priming of CD8⁺ CTL precursors in vivo to exogenous HBsAg particles. After transfer into a syngeneic, naive host, HBsAg particle-pulsed DC, either freshly purified from skin or derived from a cloned DC line, efficiently primed class I- restricted, HBsAg-specific CTL precursors. Mφ, either harvested from the peritoneal cavity or generated in macrophage-CSF-stimulated bone marrow cell cultures in vitro or derived from established, cloned Mφ lines (PU5-1.8, J774A.1), pulsed with HBsAg particles in vivo or in vitro, elicited a class I-restricted, HBsAg-specific CTL response after adoptive transfer into naive hosts. The class I-restricted CTL response induced by HBsAg particle immunization was suppressed in carrageenan-treated mice, but was restored when carrageenan-treated mice were immunized with syngeneic, HBsAg-pulsed Mφ. Selective elimination of Mφ by liposome-incorporated dichloromethylene- diphosphonat did not suppress the induction of a CTL response of H-2(d) mice by HBsAg particle immunization. HBsAg-pulsed, freshly prepared DC are more potent than pulsed Mφ in priming class I-restricted CTL in vivo. The relative importance of both types of APC in priming CTL remains to be resolved.