The pain, discomfort, or symptoms associated with the heart muscle not getting enough blood and oxygen. Angina is not typically a sharp pain like that associated with, for example, hitting your thumb, but more of a pressure-like sensation. The classic description of angina is when the patient experiences pressure, usually on the front of the chest just underneath the breast bone, or to the left of the breast bone. The discomfort can travel to the neck or down the arm. Sometimes the patient will describe some numbness of the arm. The pain is usually brought on by some kind of stress or exercise and often dissipates with rest. Angina, however, can also be confused with indigestion, gallbladder symptoms, or in some cases, flu-like symptoms. Angina is not the same as having a heart attack but can be a warning sign of a potential heart attack. Important in the body's defense against infections, an antibody is a blood protein that is produced by the body's immune system in response to a foreign body or foreign protein. These foreign bodies/proteins include bacteria, viruses, as well as other foreign tissues, such as a transplanted heart, lung, liver or kidney. Immunization against measles, mumps, and chicken pox is done to expose the body to the inactivated organism so the body can manufacture antibodies that will, in the future, recognize the live organism and help the body fight off the infection. Antibodies are very specific, so an antibody that is protective against measles won't fight off tetanus. In transplantation surgery, some medications are used to blunt the patient's immune system response to the foreign transplanted organ. Rejection of the transplant is often the result of antibodies that are formed to combat the perceived foreign tissue. The heart beats or pumps at a certain speed and in a certain way, depending on the needs of the patient's body. When the heart is pumping normally, the heart is said to be in a normal (sinus) rhythm. Any deviation from a normal rhythm is defined as an arrhythmia, where the heart is beating too fast, too slow, beating irregularly or a combination of these abnormal rhythms. Arrhythmias are generally divided between atrial arrhythmias such as atrial fibrillation and ventricular arrhythmias. Most arrhythmias can be treated with medications, but some require surgery. While most arrhythmias are not life-threatening, some, such as ventricular fibrillation, are fatal if not treated quickly. Arrhythmias can be secondary to many causes, such as heart attack, medications, and electrolyte imbalances. Also called the Landsteiner classification, the ABO blood groups classify blood into four types, A, B, AB, and O, and recognizes which blood groups can be safely mixed. Type O blood can give to all blood types, but can receive only from type O. AB blood type can give to only AB, but can receive from any group. Thus type O is sometimes called the universal donor and type AB the universal recipient. Type A can give to types A and AB and receive only from types A and O, and type B can give to types B and AB, and receive only from type B or O. An instrument used to look inside the lung's airways, which are known as a bronchus/bronchi or bronchiole, depending on the size of the airway. Most bronchoscopes consist of a flexible tube that is divided into three channels: the first channel has a fiberoptic channel that delivers light to the end of the scope; the second channel has an optic system that allows the physician to view inside the lungs; the third channel allows the physician to sample tissue, with biopsy tools or aspirate fluid from the different parts of the lungs. A bronchoscope is used to look inside the lungs to look for cancers, benign tumors, or infections, or to clear excessive fluids or mucous that may be blocking an airway. An alternative to the flexible bronchoscope, a rigid bronchoscope is a metal tube with the same components as the flexible bronchoscope, except the viewing channel is simply the opening in the metal tube. In general, most bronchoscopic exams are done using a flexible bronchoscope, with the patient under mild sedation.