Studies on pulmonary granuloma formation by Propionibacterium acnes in sarcoidosis Part 1. Interleukin-2 production and receptor expression of alveolar lymphocytes stimulated by Propionibacterium acnes in sarcoidosis

We previously reported that alveolar lymophocytes in patients with active sarcoidosis are sensitized Propionibacterium acnes (P. acnes) which may play a significant role in the induction of alveolitis in these patients. We further investigated the production of Interleukin-2 (IL-2), and the responsiveness to IL-2 of alveolar lymphocytes obtained from sarcoidosis patients and stimulated by P. acnes in vitro. In 21 untreated sarcoidosis patients, 7 treated patients and 13 control subjects, the mean IL-2 activity of fluid released from cultured alveoloar lymphocytes was 9.8±15.7 (M±SD), 1.9±4.7 and 0.2±0.8 u/ml respectively. The IL-2 activity of lymphocytes from untreated patients was significantly higher than that of control subjects (p<0.02). Neither perioheral lymphocytes in sarcoidosis patients nor in controls produced IL-2 stimulated by P. acnes. The responsiveness of alveloar lymphocytes to recombinant IL-2 was evaluated by 3H-thymidine uptake in the presence and absence of P. acnes. Lymphocytes stimulated by P. acnes showed a significantly increased uptake (3,766±3,929 dpm) compred to ustimulated lymphocytes (1,123±968 dpm) obtained from 11 untreated sarcoidosis patients (p<0.02). On the other hand, the responsiveness of lymphocytes obtained from 6 control subjects was low regardless of stimulation by P. acnes. There was a significant correlation (p<0.05) between the P. acnes-induced production of IL-2 by alveolar lymphocytes and the blastogenesis of alveloar lymphocytes in untreated sarcoidosis patietnes. Our findings indicate that P. acnes stimulated IL-2 production and IL-2 receptor induction in alveolar lymphocytes from patients with active sarcoidosis. This study supported our hypothesis that P. acnes could be an antigen causing sarcoidosis.