Tuberculosis or tuberculosis is an airborne infection caused by the inhalation of droplets containing Mycobacterium tuberculosis. When infected, the body triggers a cell-mediated hypersensitivity response that leads to the formation of a lesion or cavity and a positive reaction to the tuberculin skin test (Kaufman, 2011). People infected with mycobacteria will have a positive skin test, but only those with active tuberculosis will show signs and symptoms. Basic signs and symptoms include low-grade fever, cough with hemoptysis, and tachypnea. They may also present with pleuristic 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 by inhalation of droplet nuclei circulating in the air. These droplets are expelled from the respiratory secretions of people with active TB through coughing, sneezing and talking (Porth, 2011). Some bacilli remain in the upper respiratory tract and are cleared by goblet cells and mucus-secreting cilia on the surface of the airways. Others will escape this protective mechanism to travel and settle in the alveoli (Porth, 2011). A local inflammatory response occurs and macrophages are cells that act as a next-line defense mechanism to combat mycobacteria. First, they engulf microbacteria, attempt to reduce their strength and capabilities, and kill them. Likewise, they send the antigen to helper T lymphocytes to trigger a cell-mediated immune response (Knechel, 2009). Infected macrophages will send out cytokines and enzymes produced to break down mycobacteria proteins. These are the released cytokines that attract T lymphokines ly...... middle of paper ......d. The lymphokines will attract other inflammatory cells to the site. This response typically peaks 48 hours after PPD injection. Redness at the injection site and induration resulting from cellular infiltration represent the immune response to the skin test (Nayak, 2012). ConclusionTuberculosis is an airborne infection that primarily affects the lungs. Not all infected people show signs and symptoms. Only people with active tuberculosis experience signs and symptoms such as low-grade fever, cough with hemoptysis, tachypnea, pleuristic 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 either as a result of a previous tuberculosis infection or after receiving of BCG..