The ability of tuberculosis patients to recognize Mycobacterium vaccae-specific antigens before starting chemotherapy and according to disease severity was analyzed. We report that the M. vaccae cell wall skeleton fraction triggers more enhanced cytokine production than the whole bacterium. Moreover, a tendency was observed for a lower gamma interferon/interleukin-10 ratio in patients with cavitary disease induced by M. vaccae antigens. Copyright © 2008, American Society for Microbiology. All Rights Reserved.