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 stimulators of T cell immune responses. We investigated the requirements for antigen presentation by these cells in priming cytotoxic T lymphocyte (CTL) responses to intracellular bacterial and viral pathogens. [Parent-->F-1] radiation BM chimeras were constructed using C57BL/6 donors and (C57BL/6 X BALB/c)F-1 recipients. Infection of chimeric mice with either Listeria monocytogenes or vaccinia virus expressing the nucleoprotein (NP) antigen from lymphocytic choriomeningitis virus (LCMV) primed H2-D-b-restricted, but not H2-K-d-restricted CTL responses, demonstrating the requirement for BM-derived APCs 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- and H2-L-d-restricted NP epitopes. These findings indicate that in vivo priming of CTL responses to LCMV is remarkably insensitive to deficiencies in antigen presentation by professional BM-derived APCs.