Smoking inhibits lung's immune cells.Smoking inhibits lung's immune cellsEpidemiologic studies epidemiologic study A study that compares 2 groups of people who are alike except for one factor, such as exposure to a chemical or the presence of a health effect; the investigators try to determine if any factor is associated with the health effect indicate cigarette smokers are more susceptible than nonsmokers to respiratory infections but not to other infections. Working with rats, scientists have now found a possible biological basis for this. They report that cigarette smoke preferentially depreses the function of immune cells in lymph nodes Lymph nodes Small, bean-shaped masses of tissue scattered along the lymphatic system that act as filters and immune monitors, removing fluids, bacteria, or cancer cells that travel through the lymph system. that lie within the lung tissue, and that only prolonged smoke exposure induces changes in immune cells stored in other parts of the body. They also found that the smoke primarily affects antibody-producing B-lymphocytes rather than other immune cell types, shedding light on the mechanism of immune suppression, says study coauthor Mohan L. Sopori, an immunologist at Lovelace Medical Foundation in Albuquerque, N.M. Previous animal studies have shown cigarette-induced immune dysfunction, but these did not focus on lung-associated lymph nodes and did not reveal what types of immune cells were primarily affected. Human studies have yielded inconsistent results, probably because these studies haven't looked at the lung-associated lymph nodes, says George M. Shopp, also at lovelace. Shopp, Sopori and their co-workers exposed rats to cigarette smoke for varying time periods and compared them with two age- and sex-matched control groups. The smoke-exposed rats, strapped in restraint devices, had their noses attached to a chamber fed by a burning cigarette. Some control rats also were restrained but hooked to a smoke-free inhalation chamber. Others were treated normally. After the exposure period, the researchers removed the rats' lymph nodes to measure antibody secretion by B-cells as well as macrophage macrophage /mac·ro·phage/ (mak´ro-faj) any of the large, mononuclear, highly phagocytic cells derived from monocytes that occur in the walls of blood vessels (adventitial cells) and in loose connective tissue (histiocytes, phagocytic and T-cell function. They found that cigarette exposure for 21 weeks or more significantly depressed B-cell function in the lung-associated lymph nodes, while exposure for more than 35 weeks affected immune cells in other lymphoid tissues lymphoid tissue Cells, tissues, and organs composing the immune system, including the bone marrow, thymus, spleen, and lymph nodes. The most highly organized components are the thymus and lymph nodes, and the least organized are the cells that wander in the loose such as the spleen spleen, soft, purplish-red organ that lies under the diaphragm on the left side of the abdominal cavity. The spleen acts as a filter against foreign organisms that infect the bloodstream, and also filters out old red blood cells from the bloodstream and decomposes . The team saw no significant effect on the function of other immune cell types from the lymph nodes or the spleen, they report in the March 1 TOXICOLOGY toxicology, study of poisons, or toxins, from the standpoint of detection, isolation, identification, and determination of their effects on the human body. Toxicology may be considered the branch of pharmacology devoted to the study of the poisonous effects of drugs. AND APPLIED PHARMACOLOGY. Shopp warns that non-immune-related factors--such as the breakdown of lung tissue or emphysema emphysema (ĕmfĭsē`mə), pathological or physiological enlargement or overdistention of the air sacs of the lungs. A major cause of pulmonary insufficiency in chronic cigarette smokers, emphysema is a progressive disease that commonly -- also could contribute to smokers' increased susceptibility to respiratory infections. |
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