Leukotriene B4 receptor 1 is differentially expressed on peripheral T cells of steroid-sensitive and -resistant asthmatics

Abstract Background Numbers of CD8+ T cells expressing the leukotriene B4 (LTB4) receptor, BLT1, have been correlated with asthma severity. Objective To examine the activation and numbers of BLT1-expressing peripheral blood CD4+ and CD8+ T cells from patients with steroid-sensitive (SS) and steroid-resistant (SR) asthma. Methods CD4+ and CD8+ T cells isolated from peripheral blood of healthy human subjects and patients with SS and SR asthma were stimulated in culture with anti-CD3/anti-CD28 followed by analysis of BLT1 surface expression and cytokine production. Activation of CD8+ T cells after ligation of BLT1 by LTB4 was monitored by changes in intracellular Ca2+ concentrations. Results The number of BLT1-expressing cells was larger in patients with asthma than in controls and larger on activated CD8+ than on CD4+ T cells. Addition of LTB4 to activated CD8+ T cells resulted in increases in intracellular Ca2+ concentrations. Expansion of activated CD4+ T cells, unlike CD8+ T cells, was significantly decreased in the presence of corticosteroid. In patients with SS asthma, numbers of BLT1-expressing CD8+ T cells were lower in the presence of corticosteroid, unlike in those with SR asthma in whom cell expansion was maintained. Levels of interleukin-13 were highest in cultured CD8+ T cells, whereas interleukin-10 levels were higher in CD4+ T cells from controls and patients with SS asthma. Interferon-γ levels were lowest in patients with SR asthma. Conclusion Differences in BLT1 expression, steroid sensitivity, and cytokine production were demonstrated in T lymphocytes from patients with SS and SR asthma. The LTB4–BLT1 pathway in CD8+ cells may play an important role in asthma and serve as an important target in the treatment of patients with SR asthma.