Monocyte inflammatory protein-1 alpha facilitates priming of CD8(+) T cell responses to exogenous viral antigen.

Dendritic cells (DC) derived from bone marrow precursors of BALB/c or C57BL/6 mice in low-serum cultures supplemented with granulocyte macrophage colony stimulating factor and Flt(3) ligand were pulsed in vitro with hepatitis B surface antigen (HBsAg) particles. DC processed exogenous HBsAg and presented its MHC class I-binding epitopes to cytotoxic T lymphocytes (CTL). This specific and restricted interaction of DC with CTL stimulated release of IFN-gamma and macrophage inflammatory protein (MIP)-1 alpha from the responding CTL. MIP-1 alpha enhanced the survival of DC in vitro but did not induce proliferation. Furthermore, co-delivery of MIP-1 alpha facilitated CTL priming in vivo to exogenous HBsAg in low responder C57BL/6 (H-2(b)) mice: a single injection of a low dose of HBsAg particles (without further adjuvants) successfully primed K(b)-restricted CTL responses to HBsAg only when the exogenous antigen was co-delivered with 100 ng MIP-1 alpha. These in vitro and in vivo data point to an important role of MIP-1 alpha in the DC-dependent priming of CTL to exogenous viral antigens.