For most individuals, the lung has a remarkable ability to deal with exposure to a variety of inhaled bacteria. Some individuals, however, do have recurrent bacterial infections, usually in the form of acute or chronic bronchitis and, in some instances, pneumonia. The reasons for this variability in bacterial infections between otherwise healthy subjects, between types of lung disease, and within the same type of lung disease are poorly understood.

Variability in susceptibility to bacterial infections is partially explained by differences in exposure to infectious agents, genetic susceptibility and innate (or early) immune responses. It is of interest that the incidence and severity of bacterial infections is greatest during the winter months. Other than viral infections, there are few variables that change with season. Vitamin D is one known immune modulator with a seasonal periodicity. The hypothesis of this study is that levels of vitamin D are an important determinant of the innate defense of the lung against inhaled bacteria. The investigators further postulate that vitamin D has effects on the innate immune function of both alveolar macrophages and lung epithelial cells.

Inclusion Criteria:

Signed informed consent form Age 18 - 60 Healthy nonsmoker, healthy smoker Forced expiratory volume in 1 second (for smokers) > 60% predicted.

Exclusion Criteria:

• Pregnant or breastfeeding
• Medications (with the exception of hormonal birth control, thyroid medication or prespecified over the counter medications), including multi-vitamins and any preparation that contains vitamin D
• Asthma
• Heart disease
• Diabetes
• Previous positive tuberculin skin test, or previous diagnosis of tuberculosis
• Recent respiratory tract infection
• History of multiple bouts of pneumonia
• Allergies to caines, atropine, or a history of adverse reaction to narcotics
• Other factors that increase the risk of bronchoscopy
• Evidence of acute bronchitis within the past 2 weeks