Suppression of antitumor immunity by stromal cells expressing fibroblast activation protein-alpha.

The stromal microenvironment of tumors, which is a mixture of hematopoietic and mesenchymal cells, suppresses immune control of tumor growth. A stromal cell type that was first identified in human cancers expresses fibroblast activation protein-α (FAP). We created a transgenic mouse in which FAP-expressing cells can be ablated.

CD27 mediates interleukin-2-independent clonal expansion of the CD8+ T cell without effector differentiation.

The clonal expansion of antigen-specific CD8+ T cells in response to microbial infections is essential for adaptive immunity. Although IL-2 has been considered to be primarily responsible for this process, quantitatively normal expansion occurs in the absence of IL-2 receptor signaling. Here, we show that ligating CD27 on CD8+ T cells that have been stimulated through the T cell receptor causes their expansion in the absence of IL-2 by mediating two distinct cellular processes: enhancing cell cycling and promoting cell survival by maintaining the expression of IL-7 receptor alpha.