Requirements for bone marrow-derived antigen-presenting cells in priming cytotoxic T cell responses to intracellular pathogens

Bone marrow (BM)-derived antigen-presenting cells (APCs) are potent stimula tors of T cell immune responses. We investigated the requirements for antig en presentation by these cells in priming cytotoxic T lymphocyte (CTL) resp onses to intracellular bacterial and viral pathogens. [Parent-->F-1] radiat ion BM chimeras were constructed using C57BL/6 donors and (C57BL/6 X BALB/c )F-1 recipients. Infection of chimeric mice with either Listeria monocytoge nes or vaccinia virus expressing the nucleoprotein (NP) antigen from lympho cytic choriomeningitis virus (LCMV) primed H2-D-b-restricted, but not H2-K- d-restricted CTL responses, demonstrating the requirement for BM-derived AP Cs for successful priming of CTL responses to these pathogens. Surprisingly , this did not hold true for chimeric mice infected with LCMV itself. LCMV- infected animals developed strong CTL responses specific for both H2-D-b- a nd H2-L-d-restricted NP epitopes. These findings indicate that in vivo prim ing of CTL responses to LCMV is remarkably insensitive to deficiencies in a ntigen presentation by professional BM-derived APCs.