CD8⁺ dendritic cells (DCs) are responsible for cross-presenting antigens to CD8⁺ T cells in vivo. This process, known as cross-priming, allows CD8⁺ T cells to recognize antigens that are not expressed by professional antigen-presenting cells (APCs). The study shows that CD8⁺ DCs, but not CD8⁻ DCs, are capable of cross-presenting antigens. This was demonstrated by injecting B6 mice with β2m⁻/⁻ splenocytes loaded with ovalbumin (OVA), which are unable to present OVA in association with MHC class I molecules. However, these cells elicit OVA-specific CD8⁺ T cell responses when injected into B6 mice. The study found that host splenic DCs take up and present cell-associated OVA to CD8⁺ T cells. Analysis of the OVA-presenting DCs indicated that only lymphoid DCs, and not myeloid DCs, cross-present antigens in vivo. This result suggests that lymphoid DCs play an important and distinct role in the generation of CD8⁺ T cell responses directed towards cell-associated antigens. The cross-presentation process is TAP-dependent, indicating an endosome to cytosol transport. The study also showed that only a small fraction of lymphoid DCs present OVA to CD8⁺ T cells. These findings highlight the importance of CD8⁺ DCs in the cross-priming of CD8⁺ T cells in vivo.CD8⁺ dendritic cells (DCs) are responsible for cross-presenting antigens to CD8⁺ T cells in vivo. This process, known as cross-priming, allows CD8⁺ T cells to recognize antigens that are not expressed by professional antigen-presenting cells (APCs). The study shows that CD8⁺ DCs, but not CD8⁻ DCs, are capable of cross-presenting antigens. This was demonstrated by injecting B6 mice with β2m⁻/⁻ splenocytes loaded with ovalbumin (OVA), which are unable to present OVA in association with MHC class I molecules. However, these cells elicit OVA-specific CD8⁺ T cell responses when injected into B6 mice. The study found that host splenic DCs take up and present cell-associated OVA to CD8⁺ T cells. Analysis of the OVA-presenting DCs indicated that only lymphoid DCs, and not myeloid DCs, cross-present antigens in vivo. This result suggests that lymphoid DCs play an important and distinct role in the generation of CD8⁺ T cell responses directed towards cell-associated antigens. The cross-presentation process is TAP-dependent, indicating an endosome to cytosol transport. The study also showed that only a small fraction of lymphoid DCs present OVA to CD8⁺ T cells. These findings highlight the importance of CD8⁺ DCs in the cross-priming of CD8⁺ T cells in vivo.