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 αvβ3 and/or αvβ5 in this process. In the mouse, cross-presentation was recently shown to be a function of CD8α+ DC. Here we report that CD36 is expressed on CD8α+, but not on CD8α−, DC. To address the role of CD36 in cross-presentation we compared CD36−/− and CD36+/+ H-2b DC for their ability to stimulate naive OT-1 T cells specific for OVA plus H-2Kb 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+/+ CD8α+ 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 β3 and β5 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 β3 and β5 integrins can support the specialized cross-presenting function of CD8α+ DC.