Phagocytic dendritic cells from myelomas activate tumor-specific T cells at a single cell level

Antigen-presenting cells (APCs) from subcutaneous mouse MOPC315 plasmacytom a phagocytosed immunoglobulin G-coated magnetic beads, enabling efficient i solation within 2 hours by magnetic separation (APC-MB). Cell morphology wa s heterogeneous, with some of the cells having dendrites, The surface pheno type of purified tumor APCs-MB was CD11b(+), CD11c(+), CD40(+), CD80(+), CD 86(+), and MHC class II+. Tumor APCs-MB expressed messenger RNA for fractal kine and ABCD-1 chemokines, and for CC-type chemokine receptors CCR5 and CC R7, indicating the presence of mature dendritic cells (DCs). Visualized at a single cell level within 4 hours after disruption of the tumor, APCs-MB i nduced rapid Ca++ mobilization in MHC class II-restricted tumor idiotype (I d)-specific cloned CD4(+) T cells. In long-term assays, tumor APCs-MB induc ed proliferation of naive T cells from rd-specific T-cell receptor transgen ic mice. The results suggest that tumor APCs-MB represent a heterogeneous c ell population that includes myeloid-derived DCs of various stages of matur ation. A considerable fraction (greater than or equal to 15%) of DCs is spo ntaneously primed with tumor-specific antigen. (Blood, 2001;97:2808-2814) ( C) 2001 by The American Society of Hematology.