Induces pro-inflammatory responses (PubMed:22427668, PubMed:27481848). Induces host TLR1/2 heterodimerization, which causes an increased recruitment of IRAK1, MYD88, and protein kinase C epsilon (PRKCE) to the downstream TLR-signaling complex that translocates PRKCE into the nucleus in an IRAK1-dependent manner. PRKCE-mediated phosphorylation allowed the nuclear IRAK3 to be exported to the cytoplasm, leading to increased activation of ERK1/2, stabilization of MAPK phosphatase 1 (MKP1), and induction of TNF-alpha with concomitant down-regulation of MAP kinase p38 (PubMed:27481848). During M.tuberculosis and HIV-1 co-infection, can stimulate transcription from the long terminal repeat (LTR) of HIV-1 in monocyte/macrophage cells. Interaction with human TLR2 activates the NF-kappa-B transcription factor, which binds to the promoter region of the HIV-1 and induces HIV-1 gene expression. Interacts with LRR motifs 15-20 of host Toll-like receptor 2 (TLR2). Not secreted but surface exposed. Mainly localized in the cell wall fraction regardless of PE11 co-expression. Up-regulated under microaerophilic and anaerobic conditions, nutrient starvation and in the presence of palmitic acid (PubMed:18400969). Coexpressed with PE11 (PubMed:23469198). The N-terminal domain is essential for interaction with TLR2 and activation of HIV-1 LTR (PubMed:22427668). The PPE region contains the information necessary for targeting and anchorage to the cell wall (PubMed:23469198). Shows a strong immunoreactivity toward tuberculosis (TB) patient sera compared to that of BCG-vaccinated controls. Could be an attractive candidate for serodiagnosis to discriminate patients with active tuberculosis from BCG-vaccinated individuals. Could diagnose both pulmonary and extrapulmonary tuberculosis cases (PubMed:18400969, PubMed:26364913, PubMed:28651002). Can also be used as a novel serodiagnostic marker to detect latent tuberculosis infection (LTBI) (PubMed:30475863). Antibody responses elicited in TB patients are directed mostly towards the N-terminal domain of PPE17, suggesting that the N-terminal domain of PPE17 protein is immunodominant and could be used as a better serodiagnostic marker than the full-length PPE17 protein (PubMed:28651002). Antibodies directed against N-terminal domain of PPE17 in active TB patients do not significantly cross-react with N-terminal domains of other PPE proteins (PubMed:28651002). Belongs to the mycobacterial PPE family.