Objective

One limitation to successful cancer immunotherapy is the failure of lymphocytes to effectively infiltrate solid tumours. Furthermore, once within tumours, anti-tumour T cells are suppressed by Foxp3+ Regulatory T cells (Treg), which are highly enriched at the tumour site. We have found that depletion of Treg serves two purposes, which link to promote control of tumour growth. Firstly, Treg depletion results in robust immune activation and the induction of anti-tumour immune responses. Secondly, Treg-depletion can result in intra-tumoural neogenesis of specialised blood vessels, named high endothelial venules (HEV) normally found only found in secondary lymphoid organs. Development of these vessels is intricately linked to immune activation and their presence serves to increase the frequency of tumour-infiltrating T cells and improve control of tumour growth. These findings could inform future therapeutic approaches to increase access of effector cells to the tumour microenvironment