The invention relates to an immunotherapeutic agent based on cell wall fragments Mycobacterium tuberculosis useful for the combined treatment of tuberculosis with other anti¬tuberculosis drugs. It relates also to a process for preparing the immunotherapeutic agent by culturing a pathogenic strain of Mycobacterium tuberculosis for a specific period of time and homogenizing the culture in the presence of a non-ionic surfactant. The immunotherapeutic agent shows synergism when combined with other anti-tuberculosis drugs for the treatment of tuberculosis.