This study will utilize memory immune responses as search tools for the 'immunological imprints' from P. acnes or Mtb exposure. Peripheral blood mononuclear cells and bronchoalveolar cells will be compared from patients with stage II and/or stage III sarcoidosis and from healthy control subjects. Investigators will use ELISPOT assay to study: (1) frequencies of pathogen-specific interferon-7 and interleukin-10-producing cells, and (2) utilizing P. acnes- or Mtb-infected autologous monocytes and alveolar macrophages as target cell frequencies of pathogen-specific granzyme B-releasing cytotoxic T lymphocytes and natural killer cells. Finally, investigators will test the feasibility of identifying by DNA micro array, pathogen specific, transcriptional host gene expression profiles in P. acnes- and Mtb-stimulated blood cells from healthy control subjects and patients with active sarcoidosis and to compare these with gene expression profiles from autologous, unstimulated in situ lung cells. The studies will address the role of P. acnes and Mtb in the etiology of sarcoidosis and will also serve as a basis or model for future work involving other possible infectious or non-infectious pathogens/antigens for the development of sarcoidosis.