10.22376/ijpbs.2019.10.1.p1-12 Volume 3 Issue 4 2012(October - December) Toll-like receptors (TLRs) are a family of germline-encoded pattern-recognition receptors involved in recognizing diverse molecular patterns of the invading pathogens called pathogen associated molecular patterns (PAMPs). TLRs play an important role as regulators of innate and adaptive immune responses in fishes. TLRs specifically recognize the ligands and activate various cascades of pathways to destroy the pathogens. About 17 different TLR types (TLR 1, 2, 3, 4, 5, 5S, 7, 8, 9, 13, 14, 18, 19, 20, 21, 22, 23) have been identified in teleost fishes with specificity in identifying the ligands. Studies on the expression profiles of TLR18 in teleost fishes are scanty. Hence, this study was carried out with an objective to assess the expression profile of TLR18 in lessThan i greaterThan Pangasius pangasius lessThan /i greaterThan (a freshwater cat fish species) by inducing with lessThan i greaterThan Edwardsiella tarda lessThan /i greaterThan , a gram-negative bacterial pathogen infecting fish. Real-time quantitative PCR analysis was performed to study the differential expression of TLR18 in skin, gill, , liver, intestine, kidney and spleen tissue of lessThan i greaterThan P.pangasius lessThan /i greaterThan . The results of real-time quantitative PCR analysis showed differential and induced expression of TLR18 in various tissues of lessThan i greaterThan P.pangasius lessThan /i greaterThan at various time intervals, 2h, 6h, 24h and 48h post exposure with lessThan i greaterThan E.tarda lessThan /i greaterThan . JAWAHAR RAJ. K,UMA. A AND REBECCA. G Toll-like receptors, pathogen recognition receptors, mRNA expression, Real time quantitative PCR 1016-1021