C5 and tuberculosis: In our previous studies, MTB peptides E6 and E7 from early secreted antigenic target-6 (ESAT-6) and C14 from culture filtrate protein-10 (CFP-10) were confirmed as HLA-DR-restricted and specific TCR ligands of CD4+ T cells, while C5 from CFP-10 was identified as a specific TCR ligand of both CD4+ T cells that is restricted by HLA-DR and CD8+ T cells by testing PBL and pleural fluid (PLF) samples from active TB patients using the IFN-γ-enzyme-linked immunospot (IFN-γ-ELISPOT) assay, lymphocyte-proliferation and -blocking tests, and intracellular cytokine staining (ICS).