CD36 or αvβ3 and αvβ5 integrins are not essential for MHC class I cross-presentation of cell-associated antigen by CD8α+ murine dendritic cells

Cross-presentation of cell-associated Ag is thought to involve receptor-mediated uptake of apoptotic cells by dendritic cells (DC), and studies with human DC strongly implicate the endocytic receptor CD36 and the integrins alpha(v)beta(3) and/or alpha(v)beta(5) in this process. In the mouse, cross-presentation was recently shown to be a function of CD8alpha(+) DC. Here we report that CD36 is expressed on CD8alpha(+), but not on CD8alpha(-), DC. To address the role of CD36 in cross-presentation we compared CD36(-/-) and CD36(+/+) H-2(b) DC for their ability to stimulate naive OT-1 T cells specific for OVA plus H-2K(b) in the presence of OVA-loaded MHC-mismatched splenocytes as a source of cell-associated Ag for cross-presentation. Surprisingly, no difference was seen between CD36(-/-) and CD36(+/+) CD8alpha(+) DC in their ability to cross-present cell-associated OVA or to capture OVA-bearing cells. Furthermore, the proliferation of CFSE-labeled OT-1 cells in response to OVA cross-presentation in vivo was normal in CD36(-/-) bone marrow chimeras, also arguing against a necessary role for CD36 in cross-presentation by DC or other APC. DC doubly deficient for beta(3) and beta(5) integrins were similarly unimpaired in their ability to cross-present OVA-bearing cells in vitro. These data demonstrate that in the mouse, receptors other than CD36 or beta(3) and beta(5) integrins can support the specialized cross-presenting function of CD8alpha(+) DC.