Intracellular cytokine profile of T lymphocytes in patients with chronic obstructive pulmonary disease

Abstract

Chronic obstructive pulmonary disease (COPD) is characterized by an excessive inflammatory response to inhaled particles, mainly tobacco smoking. T lymphocytes are important regulatory cells that secrete several cytokines and participate actively in this inflammatory response. According to the pattern of cytokines secreted, the immune response is classified as cytotoxic or type 1 [interferon (IFN)-gamma-, interleukin (IL)-2-dependent] and humoral or type 2 (IL-4-, IL-5-, IL-10- and IL-13-dependent). This paper sought to compare the intracellular profile of cytokine expression determined by flow cytometry in T lymphocytes harvested from bronchoalveolar lavage (BAL) and peripheral blood in patients with COPD, smokers with normal lung function and never smokers. We found that BAL T lymphocytes from COPD patients had a higher percentage of positive stained cells for most of the cytokines analysed when compared to never smokers or smokers with normal lung function. Differences reached statistical significance for IL-4, IL-10 and IL-13, particularly in CD8(+) T cells. Furthermore, the expression of most of these cytokines was related inversely to the degree of airflow obstruction present suggesting local activation and/or selective homing of T lymphocytes to the lungs in COPD patients. These observations were not reproduced in circulating T lymphocytes. These results suggest that BAL T lymphocytes in patients with COPD produce more cytokines than in controls and tend to show a type 2 pattern of intracellular cytokine expression, particularly a Tc-2 profile. This is related inversely to the degree of airflow obstruction present.

Fig 1

Flow cytometry analysis of bronchoalveolar lavage fluid (BALF) T lymphocytes staining positive for intracellular interleukin (IL)-2, interferon (IFN)-γ, Il-4 and IL-13 cytokines. CD4⁺ T (CD3⁺CD8⁻) and CD8⁺ (CD3⁺CD8⁺) lymphocytes were previously gated on a side versus CD3 positive dot plot. Positive staining was established above the background level (dotted line) of cells stained with isotype-matched phycoerythrin-conjugated monoclonal antibodies and non-stimulated samples.

Fig 2

Percentage (mean ± s.e.m.) of bronchoalveolar lavage (BAL) CD4⁺ (a) and CD8⁺ T lymphocytes (b) with positive intracellular staining for the different cytokines studied in patients with chronic obstructive pulmonary disease (COPD) (dark columns), smokers with normal lung function (grey columns) and never smokers (white columns). †P < 0·05 COPD versus non-smokers; *P < 0·05 COPD versus smokers with normal lung function.

Fig 3

Correlation analysis between the percentage of CD4⁺ (a) and CD8⁺ (b) bronchoalveolar lavage (BAL) T lymphocytes with positive intracellular staining for type 2 cytokines [interleukin (IL)-4, IL-10 and IL-13] and the degree of airflow obstruction [forced expiratory volume in 1 s (FEV₁), % reference] in smokers [with and without chronic obstructive pulmonary disease (COPD)].

Fig 4

Percentage (mean ± s.e.m.) of circulating CD4⁺ (a) and CD8⁺ T lymphocytes (b) with positive intracellular staining for the different cytokines studied in patients with chronic obstructive pulmonary disease (COPD) (dark columns), smokers with normal lung function (grey columns) and never smokers (white columns). ††P < 0·01 non-smokers versus smokers with normal lung function; *P < 0·05 COPD versus smokers with normal lung function.