Sarcoidosis--a gleam of light?

Abstract

As we approach the centenary of Besnier's description of sarcoidosis,' the enigma of sarcoidosis remains unresolved. That the challenge of the disease is still being faced is amply confirmed by three recent publications.2-4 Of all the recent major advances in our understanding of sarcoidosis, the recognition that it is not an anergic disease is probably the most important.5 The idea that the bronchoalveolar immune response may be separate from any systemic immune response has allowed clarification of many of the seemingly bizarre responses found in sarcoidosis.68 The systemic immune responses are characterised by low numbers of circulating lymphocytes, a low percentage of circulating thymus-processed lymphocytes (T cells), hypergammaglobulinaemia, and a correlation with in vivo anergy to skin-test antigens, particularly tuberculin.910 That the reduction in circulating T cells is reversible has been shown in vitro by incubation with levamisole.'0 In addition, analysis of the subpopulations of circulating T lymphocytes has suggested an imbalance between the controlling T cells-"suppressor" in function-and the helper T cells, which are usually present in normal numbers."X Probably the increased activity of T suppressor cells is mediated by circulating immune complexes present in 60% of sera from patients with sarcoidosis.'2 The contrast between the systemic immune response and the local pulmonary response is striking, for both the proportion and the number of T lymphocytes in bronchoalveolar lavage fluid are significantly greater than in controls.'3"4 On average, there are 10 times more lymphocytes in the bronchoalveolar lavage fluid of patients with sarcoidosis than in that of normal controls. There is also an increase in the number of alveolar macrophages but there is now a lower ratio of alveolar macrophages to lymphocytes.'5 These observations have led to comparisons between lavage yields, radiographic staging, and the clinical course of the disease. There appears to be little relation between the cellular content of lavage fluid and radiographic stage (stage I-bilateral hilar lymphadenopathy; stage II-bilateral hilar lymphadenopathy and pulmonary infiltrates; stage III-pulmonary infiltrates), but French workers