Objective To study an identified leucine-rich repeats(LRRs)protein,LRR containing 19(LRRC19),and to determine the distribution,localization,and biological function of LRRC19 mRNA expression in spleen cells.Methods Bioinformatics analysis was used to predetermine the structure of LRRC19 gene and protein.The distribution and localization of LRRC19 mRNA expression were detected by hybridization in situ with LRRC19 mRNA specific probes and reverse transcriptase polymerase chain reaction(RT-PCR).Additionally,the activity of secreted alkaline phosphatase(SEAP)was detected for analyzing the nuclear factor-kappa B(NF-?B)activation in HEK293T cells transfected with the expression vector of LRRC19 in vitro.Results LRRC19 was found to be a transmembrane protein,with 4 LRR motifs,a single transmembrane domain and two phosphorylation sites of casein kinase 2(CK2)at cytoplasmic domain,as analyzed through bioinformatics soft wares.Previous study revealed that LRRC19 without cytoplasmic Toll/IL-1 receptor(TIR)domain could activate NF-?B to enhance the expression of proinflammatory cytokines.LRRC 19 could also be demonstrated by ectopic expression in RAW264.7 cells after transfection with murine LRRC19 expression plasmid pcDNA3.1-V5-LRRC19 indicating that it was a transmembrane protein.In persent study,the results of hybridization in situ and RT-PCR showed that LRRC19 mRNA was expressed in the germinal center and splenic cord of mouse spleen.Additionally,LRRC19 was predominantly expressed in CD5+ lymphocyte,known as B1 cell.In vitro study also indicated that several pathogens might significantly enhance the NF-?B activity of the cells transfected with LRRC19.Conclusion LRRC19 might be a transmembrane receptor,and it may be able to recognize the conserved sequence of pathogens,participate in the induction of cell signaling,activate the NF-?B signal pathway,promote transcription of target genes,and modulate the innate immune response.