CRITICAL ROLE DISCOVERED FOR INNATE
IMMUNITY IN LUNG TRANSPLANT REJECTION
Researcher investigators have identified a critical role that innate immunity plays in lung transplant rejection which they believe has important implications for patients. (Innate immunity is the process that performs a major role in host defense during the early stages of infection because it involves the recognition of invading pathogens or "foreign" substances.) The medical scientists analyzed deoxyribonucleic acid (DNA) from 174 lung transplant recipients and 157 of their cadaver donors. The study authors point out that cardiac/pulmonary surgery, without or without cardiopulmonary bypass, has been shown to increase circulating endotoxin levels. (Endotoxins are heat stable toxins associated with the outer membrane of certain gram negative bacteria.) Endotoxins serve as a prototypical trigger of innate immunity by interacting with toll-like receptor 4 (TLR4) to recruit and activate the cellular materials necessary for an appropriate adaptive response by the body. The researchers said their results suggest that activation of innate immunity in lung transplant recipients through TLR4 contributes to the development of acute rejection after lung transplantation. They believe therapies directed at the inhibition of innate immune responses mediated by TLR4 may represent a novel and effective means of preventing acute rejection after lung transplantation. The study appears in the second issue for September 2003 of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine.
PRESCHOOL CHILDREN WITH ASTHMA
TESTED FOR PULMONARY FUNCTION
In one of the first pulmonary function studies to compare preschool children with asthma to healthy controls of similar age, French researchers, using tests that did not require active cooperation, compared the results of 74 children with asthma to those of 84 healthy youngsters. They determined that the pulmonary function test data were correlated with the clinical characteristics of asthma; they also investigated the bronchodilator response threshold that may separate children with asthma from normal preschoolers. They point out that airway resistance values were significantly higher in children with asthma regardless of whether or not they were exerting themselves. They also note that pulmonary function tests in children with asthma correlated with test scores for severity and pulmonary function in adult asthmatics. They explain that, because of their age, children frequently have trouble carrying out conventional pulmonary test maneuvers. Therefore, such tests are rarely performed in clinical practice even if they might help the child achieve as close to a normal lung function as possible. Hence, for the research, investigators used pulmonary function tests that did not required active cooperation on the part of the children. The average age of participants at asthma onset was 1.9 years and 46 percent of the 74 asthmatics had experienced their first symptoms before age 2. All of the preschoolers with asthma had moderately severe illness and 85 percent of the youngsters used daily inhaled steroid therapy. The study is published in the second issue for September 2003 of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine.
PATIENTS WITH APNEA SHOW PERIODS OF STABLE SLEEP
In sleep lab tests of 82 persons with sleep apnea, a medical scientist observed that about 82 percent of the patients with apneas had periods of stable breathing which lasted 3 minutes or more without air intake pauses. Periods of stable breathing were twice as likely to occur when patients were lying on their side rather than on their back. A Canadian investigator reported on the relationship between periods of stable breathing, which showed patient's compensated breathing, and other variables known to make upper airways even more unstable. These included growing older, male gender, increasing weight, supine sleeping, and rapid eye movement (REM) sleep. According to the National Institutes of Health, more than 12 million Americans suffer from sleep apnea. As a result of this problem, a person repeatedly stops breathing for more than 10 seconds. These pauses decrease oxygen in the blood and increase the amount of carbon dioxide. After a period without inspiration, failure to breathe triggers the patient's brain to reinitiate breathing. Usually, the arousals cannot be remembered by the person in the morning. During the test, the study investigator continuously measured air flow, body position, sleep state, and other factors. He pointed out that most people can adequately compensate for abnormal breathing mechanics, at least part of the time. The study appears in the second issue for September 2003 of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine.
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