Background: Sarcoidosis is generally characterized by a CD4+ lymphocyte predominance in bronchoalveolar lavage fluid (BALF), whereas in extrinsic allergic alveolitis (EAA) a CD8+ lymphocyte predominance is found. However, we have previously demonstrated an increase in CD4+ lymphocytes in BALF obtained from EAA patients as well. The aim of this study was to evaluate whether in sarcoidosis and EAA the BALF cellular profile-even without the help of cytokine detection-might reflect differences in the CD4+ T-lymphocyte subpopulations, i.e. T helper (TH)-1 and TH2 lymphocytes.
Methods: For this purpose, we analyzed BALF analysis results obtained from 77 nonsmoking patients with histologically proven sarcoidosis and 54 nonsmoking patients suffering from EAA.
Results: Patients with EAA showed the highest mean absolute numbers of lymphocytes, CD8+ as well as CD4+ T lymphocytes, whereas the percentage of CD4+ T lymphocytes in BALF was low. In contrast, patients with sarcoidosis showed the lowest absolute and relative number of CD8+ T lymphocytes, the highest percentage of CD4+ T lymphocytes and CD4+/CD8+ ratio. Moreover, patients with Löfgren's syndrome demonstrated an alveolitis suggesting a TH1 lymphocyte-subset-like predominant related profile, characterized by lower numbers of eosinophils and mast cells, whereas sarcoidosis patients with respiratory symptoms formed a more mixed TH1/TH2 pattern. Patients with EAA showed a cellular BALF profile suggesting a functional predominance of TH2 lymphocytes.
Conclusion: These preliminary data suggest a different distribution of the CD4+ T lymphocyte subtypes characterized by a functional heterogeneity of CD4+ T lymphocytes between-as well as within-these various pulmonary disorders. The exact role of this imbalance of TH1 and TH2-like activity in the lung with regard to the pathogenesis and prognosis needs to be further elucidated.