Tuberculosis or tuberculosis is an airborne infection caused by inhaled droplets that contain mycobacterium tuberculosis. Once infected, the body initiates a cell-mediated hypersensitivity response that leads to the formation of lesions or cavities and a positive tuberculin skin test reaction (Kaufman, 2011). People who have been infected with mycobacteria will have a positive skin test, but only those who have active tuberculosis will show signs and symptoms. Basic signs and symptoms include mild fever, cough with hemoptysis, and tachypnea. They may also exhibit pleural chest pain, dyspnea, progressive weight loss, fatigue, and malaise (Porth, 2011). Signs and Symptoms of Active Tuberculosis Mycobacterium tuberculosis (MT) is a thin, rod-shaped, aerobic bacillus that causes tuberculosis. Tuberculosis (TB) is an airborne infection that is transmitted through inhalation of droplet nuclei circulating in the air. These droplets are expelled from the respiratory secretions of people with active tuberculosis through coughing, sneezing and talking (Porth, 2011). Some bacilli remain in the upper airways and are swept away by goblet cells and cilia that secrete mucus onto the surface of the airways. Others will escape this protective mechanism to travel and settle in the alveoli (Porth, 2011). A local inflammatory reaction occurs and macrophages are cells that act as a subsequent defense mechanism to fight the mycobacteria. First they engulf the mycobacteria, try to reduce their strength and capacity and kill them. They similarly deliver antigen to helper T cells to initiate a cell-mediated immune response (Knechel, 2009). The infected macrophages will send the cytokines and enzymes produced to degrade the mycobacterial proteins. It is the released cytokines that attract the T lymphokines...... middle of paper ......d. The lymphokines will attract other inflammatory cells to the site. This response generally peaks within 48 hours of PPD injection. Redness at the injection site and induration resulting from cellular infiltration represent the immune response to the skin test (Nayak, 2012). Conclusion Tuberculosis is an airborne infection that primarily affects the lung. Not all infected people show signs and symptoms. Only people who have active tuberculosis show signs and symptoms such as mild fever, cough with hemoptysis, tachypnea, pleural chest pain, dyspnea, progressive weight loss, fatigue, and malaise. The PPD skin test is one way to detect mycobacterial infection. A positive PPD skin test is the result of a specific immune response against the antigen introduced into the skin of a person who has been exposed to mycobacteria from either previous tuberculosis or BCG infection.