YOSHIKO IWAI ET AL: 'PD-1 blockade inhibits hematogenous spread of poorly immunogenic tumor cells by enhanced recruitment of effector T cells.', INTERNATIONAL IMMUNOLOGY, vol. 17, no. 2, 20 December 2004 (2004-12-20), pages 133 - 144, XP055142463, ISSN: 0953-8178, DOI: 10.1093/intimm/dxh194