Gamma/delta T lymphocytes in the BCG granulomatous lesions

Abstract

Recent studies in man and animal models have demonstrated that TCR-γδ-bearing T cells (γδ T cells) are activated by mycobacteria and accumulate in the sites of mycobacterial infection. Although the function of γδ T cells remains unclear, some data suggest a potential role for these cells in the granulomatous immune response. To address the presence of γδ T cells within the BCG granulomas, we have characterized the TCR phenotype of T-lymphocytes present in the BCG granulomatous lesion immunohistochemically using a monoclonal antibody to TCR δ1 and others. Fairly large numbers of γδ T cells were located at the periphery of the BCG granulomas without necrosis and most of them also expressed CD8. However, γδ T cells were rarely present in the granulomas with central caseous necrosis, calcification and fibrotic changes. With these results, it might be speculated that the CD8+ γδ T lymphocytes participate in the BCG granuloma formation mainly in the early stage.