Study of T-Regulatory Cells in Asthma

The investigators hypothesize that the increase in asthma severity in obese patients is, at least in part, related to a defective number or function of regulatory T cells (Tregs). That is in the obese asthmatic subject a defective Treg profile would augment the inflammation of asthma (a synergistic effect). Alternatively, that Treg dysfunction in obesity might affect asthma independently (an additive effect). To test these hypotheses, the investigators plan to conduct an observational controlled study to compare Treg profile in obese and normal-weight individuals with and without asthma.

This is an exploratory study to investigate the following:

• To determine whether Treg number and function differs between obese and normal-weight individuals with and without asthma.
• To determine whether serum leptin levels differ between obese and normal-weight individuals with and without asthma.

Inclusion criteria

• Obese asthmatics
• Normal weight asthmatics
• Healthy obese
• Health non-obese

Asthmatic subjects will be recruited:

• If they have a physician diagnosis of adult onset asthma (asthma diagnosed after the age of 18).
• If they have stable disease without exacerbation, physician or emergency department visits, or change in asthma medication for the past 4 weeks, inhaled steroids will be allowed.

Non asthmatic subjects

• Will not have had a prior diagnosis of asthma,
• Have no history of atopy.
• Have no history of lung diseases.

Exclusion criteria

• > 10 pack year smoking history, or currently smoking
• Pulmonary disease other than asthma.
• History of heart disease
• Weight loss greater than 10 kg, or greater than 10% initial body weight within the past 3 months.
• Any agents that could potentially alter the inflammatory system such as thiazolidinedione, a statin, or oral steroid therapy.