Blood group antigens are carbohydrates that are attached to proteins or lipids. An antigen is a substance foreign to the body that causes an immune response. An immune response occurs when antibodies, which are proteins in your immune system, are summoned to attack an antigen.
Blood that reaches the lungs travels throughout a network of small blood vessels, where oxygen moves into the blood and carbon dioxide moves out of the blood, according to the National Heart, Lung and Blood Institute.
How COPD Affects Breathing. When your lungs are healthy and work properly, the air you breathe moves freely in and out. Inside your lungs are airways, which are called bronchial (BRONK-ee-ol) tubes. The airways branch into clusters of air sacs called alveoli (AL-vee-OL-ee). When you breathe in fresh air, it moves into the air sacs, where oxygen is absorbed into the blood stream and carried to all parts of your body. The air sacs also remove carbon dioxide from the blood. When you breathe out, stale air with carbon dioxide passes out of your airways and lungs.