Cellular recognition of Mycobacterium tuberculosis ESAT-6 and KatG peptides in systemic sarcoidosis

Abstract

Sarcoidosis is an enigmatic disease with a pathology similar to that of tuberculosis. We detected Th-1 immune responses to Mycobacterium tuberculosis ESAT-6 and KatG peptides from peripheral blood mononuclear cells from 15/26 sarcoidosis, 1/24 purified-protein-derivative-negative (PPD-) (P < 0.0001, Fisher's exact test), and 7/8 PPD-positive (PPD+) subjects (P = 0.21). This finding provides immunologic links between mycobacteria and systemic sarcoidosis.

FIG. 1.

Distribution of T-cell frequencies for PPD− control, PPD+, and sarcoidosis subjects for KatG peptide 13. The bars represent the 25th percentile, median (50th percentile), and 75th percentile for each group; for PPD− controls, these three quantities are all equal to zero. The PPD+ group included the greatest percentage of study participants recognizing KatG peptide 13 as well as the highest median T-cell frequency. Although the sarcoidosis subjects are PPD− and have no culture evidence of infection by mycobacteria, the distribution of the T-cell frequencies for the sarcoidosis subjects was significantly different from that for the PPD− controls (P < 0.0001) and was closer to that for the PPD+ subjects (P = 0.17).

FIG. 2.

Distribution of T-cell frequencies for the PPD− control, PPD+, and sarcoidosis subjects for ESAT-6 peptide 14. The bars represent the 25th percentile, median (50th percentile), and 75th percentile for each group; for PPD− controls, these three quantities are all equal to zero; for sarcoidosis subjects, the 25th percentiles and medians are both equal to zero. Although all of the sarcoidosis subjects tested were PPD−, there was a significant difference in the distribution of the T-cell frequencies for the sarcoidosis and PPD− subjects (P = 0.024). The lone PPD− subject who recognized ESAT-6 peptide 14 had a T-cell frequency comparable to those for the sarcoidosis and PPD+ subjects. Comparison of the sarcoidosis and PPD+ subjects revealed that there was no significant difference in the distributions of the T-cell frequencies for ESAT-6 peptide 14 (P = 0.27).