Lung Macrophage Populations and Functions in Chronic Obstructive Pulmonary Disease (COPD)-Susceptible Smokers

Inclusion Criteria:

* Ages between 40 to 75 years old.
* History of at least 20 pack-years of smoking.
* No diagnosis of COPD or asthma.
* No spirometric evidence of airflow obstruction as determined by FEV1/FVC ratio ≥0.7.
* FEV1 and FVC \>lower limit of normal.
* Less than 1 pack-year history of tobacco smoking and no tobacco use within the past 12 months.
* Subjects will be divided into two groups by their RV/TLC:

Normal RV/TLC Group:

• Plethysmographic RV/TLC equal or less than lower limit of normal.

Abnormal RV/TLC Group:

• Plethysmographic RV/TLC higher than lower limit of normal.

Exclusion Criteria:

* Any history of IV drug use or inhalation of recreational drugs other than marijuana: A- within the past 20 years. B- more than 100 times IV drug usage. C- longer than 1 year usage.
* Marijuana use \>400 joints in lifetime or any within past 6 months.
* Inability to walk briskly, run on treadmill, or pedal on ergometer to perform the study-required exercise level.
* Pregnant/breast feeding.
* Serious and active heart conditions- defined by stable or unstable angina, recent myocardial infarction (within the last 2 years), active congestive heart failure, ischemic cardiomyopathy.
* Liver cirrhosis.
* History of chronic active Hepatitis B or C.