Plays a major role in RD1-associated pathogenesis, and may contribute to the establishment and maintenance of M.tuberculosis infection. Together with PE35, stimulates the secretion of IL-10 and MCP-1 from human macrophages, via the interaction with human Toll-like receptor 2 (TLR2) (PubMed:24467650). Stimulates high levels of gamma interferon secretion in peripheral blood mononuclear cells isolated from tuberculosis patients, as well as from healthy tuberculin purified protein derivative-positive donors. Does not interfere with the secretion and immunogenicity of EsxA (ESAT-6) and EsxB (CFP-10) (PubMed:14573626, PubMed:15039340). Homodimer (PubMed:17433643). Interacts with PE35. PE35/PPE68 complex interacts with human TLR2 (PubMed:24467650). Interacts in vitro with EspG1, EccA1 and EsxB (PubMed:17433643). Detected predominantly in the membrane and cell wall fractions. Inactivation does not abolish EsxA secretion, EsxA-specific immunogenicity and enhanced virulence. PPE68 is recognized by antigen-specific T-cell lines from HLA-heterogeneous subjects. Peptide P9 is an immunodominant and HLA-DR promiscuous peptide of PPE68 (amino acids 121-145), and may be exploited as a peptide-based vaccine candidate against tuberculosis and other mycobacterial diseases. Belongs to the mycobacterial PPE family.