Analysis of Responses of Peripheral Blood Lymphocytes From Sarcoidosis Patients to Purified Protein Derivative

Abstract

Purpose: Negative skin test reaction against purified protein derivative (PPD) is one of the important diagnostic criteria for sarcoidosis. The purpose of this study was to investigate the relationship between negative skin test reaction against PPD and the responses of peripheral blood lymphocytes (PBLs) against PPD in sarcoidosis patients. Methods: Sarcoidosis patients (n = 14) with ocular changes were selected for this study. As a control, blood was collected from volunteers without uveitis (n = 10). All subjects in both groups had a history of bacille de Calmette-Guerin vaccination, and 8 of the 14 patients underwent the PPD skin test. Peripheral blood lymphocytes were obtained from all patients and separated by gradient centrifugation. Peripheral blood lymphocytes were tested for their proliferative responses to PPD. To determine the frequency of PPD-specific precursor cells in blood, limiting dilution analysis was used. The frequency was calculated following the Poisson model. The culture supernatants were harvested 3 days after incubation and assayed for interferon (IFN)-γ production by ELISA. Results: Four of the 8 patients showed a negative skin test reaction against PPD, while all the healthy volunteers had a positive reaction. Compared to PBLs from healthy volunteers, PBLs from sarcoidosis patients showed weaker responses to PPD. There was no clear difference between these two groups about frequency of precursor cells against PPD and production of IFN-γ. Conclusions: Negative skin test for PPD in sarcoidosis patients does not seem to have any relationship to the low precursor frequency of PPD-specific cells in patient blood.