Secretion of the eosinophil‐active cytokines interleukin‐5, granulocyte/macrophage colonystimulating factor and interleukin‐3 by bronchoalveolar lavage CD4+ and CD8+ T cell lines in atopics asthmatics, and atopic and nonatopic controls

Abstract

Specific eosinophil accumulation and activation within the asthmatic bronchial mucosa are thought to occur at least partly through the actions of cytokines, including interleukin (IL)‐5, IL‐3 and granulocyte/macrophage colonystimulating factor (GM‐CSF). Although mRNA encoding some of these cytokines has been demonstrated in bronchoalveolar lavage (BAL) fluid cells and bronchial biopsies from asthmatics, it has yet to be established whether these cells produce the translated products and whether expression is associated with CD4⁺ T helper or CD8⁺ cytotoxic T cells. We addressed this problem by raising polyclonal CD4⁺ and CD8⁺ T cell lines from the BAL fluid of six atopic asthmatics, five atopic non‐asthmatics and seven non‐atopic non‐asthmatic controls. BAL fluid cells obtained at fiberoptic bronchoscopy were depleted of adherent cells, and then T lymphocytes expanded by stimulation with monoclonal anti‐CD3 antibody and recombinant human IL‐2. When lymphocytes had expanded to sufficient numbers, CD4⁺ and CD8⁺ cells were separated by positive selection with magnetic beads coated with anti‐CD4 or anti‐CD8 monoclonal antibodies and further expanded. Cytokine secretion by standardized cell numbers was measured by enzyme‐linked immunosorbent assays. BAL CD4⁺ T cell lines from the asthmatics secreted significantly elevated quantities of both IL‐5 and GM‐CSF as compared with lines from the atopic and non‐atopic controls (p = 0.023–0.003). In contrast, IL‐3 secretion did not significantly differ between the groups. In some subjects, CD8⁺ T cell lines also secreted significant quantities of these cytokines and there was a trend for IL‐5 secretion by these cells to be higher in asthmatics than non‐atopic controls (p = 0.035). These data are consistent with the hypothesis that activated T lymphocytes from asthmatics, particularly of the CD4⁺ subset, are predisposed to release elevated quantities of cytokines relevant to the accumulation and activation of eosinophils.