CD8 alveolitis in sarcoidosis: incidence, phenotypic characteristics, and clinical features

Although the accumulation of CD4 cells in the lung and other involved tissues is regarded as the distinctive immunologic feature of sarcoidosis, a few sarcoid patients can present with CD8 alveolitis. This study evaluates the incidence as well as the clinical and immunologic features of sarcoidosis presenting with CD8 alveolitis.

A total of 2,214 consecutive bronchoalveolar lavage (BAL) specimens obtained from 481 patients with sarcoidosis between January 1985 and December 1991 were retrospectively analyzed. Subjects who entered the study had the following characteristics: (1) lymphocyte alveolitis and (2) lung CD4/CD8 ratio less than 1.0. Only data obtained from patients with a first episode of pulmonary involvement were included in the analysis (394 patients).

Fifteen of the 394 patients studied at the time of diagnosis showed CD8 alveolitis as the presenting manifestation; the incidence of this phenomenon was 3.8%. A follow-up study of BAL T-cell subsets demonstrated that patients who showed high-intensity CD8 alveolitis at the onset of the disease maintained the CD8 pattern of alveolitis during relapses. Phenotypic analysis of lung T cells revealed that the accumulation of CD8 lymphocytes was due to the discrete local increase of CD45RO+ "memory" cells equipped with a number of accessory structures, including adhesion molecules and class II major histocompatibility complex-related HLA-DR antigen.

The accumulation of CD8 cells in the sarcoid lung is likely to reflect a homing of memory cells due to the ongoing immunologic response against the unknown antigen causing the disease. Although CD8 alveolitis can be considered a relatively rare event in sarcoidosis, the possibility that an increase of CD8 cells in the BAL fluid might be sustained by an underlying sarcoid inflammatory process should never be dismissed on clinical grounds in patients with interstitial lung disease.