The incidence of tuberculosis in the United States has increased during the past 10 years and tuberculOsis continues to be a significant public health problem world wide. Most individuals who are infected with Mycobacterium tuberculosis develop a cell mediated immune response and control the disease. Infected individuals stand a 10% lifetime chance of the disease reactivating. Conventional wisdom has attributed reactivation to a temporary suppression Of the immune response which allows the microorganisms to grow. Among the factors thought to be responsible for reactivation of Mycobacterial growth are infection with the human immunodeficiency virus, immunosenesence due to aging, protein malnutrition associated with chronic alcoholism and stress. The purpose of this investigation is to evaluate the effects of stress on the reactivation of Mycobacterium tuberculosis growth in a mouse model. We will test the hypothesis that stress serves as a cofactor in reactivation by altering T cell and macrophage mediated control of Mycobacterial growth. Our specific aims are: l. To determine the effect of restraint stress on reactivation of the growth of Mycobacterium tuberculosis; 2. To determine the changes in T cell mediated immunity as a result of restraint stress that results in the growth of Mycobacterium tuberculosis, and 3. To determine the changes in macrophage mediated control of Mycobacterium tuberculosis growth that results from restraint stress.