Abstract: Objective: To study the synthesis, assembly, transportation and expression of cell surface and soluble HLA B27 molecules in human lymphoblastoid cell line C1R. Methods: B27 and soluble B27 （sB27） cDNA were cloned into eukaryotic expression vector RSV.5neo and transfected into C1R cells through electroporation. Monoclonal antibodies were used in experiments such as immunoprecipitation, pulse chase and endoglycosidase H digestion to study the cell biology of B27 and sB27 molecules and their association with molecular cheparones Calnexine and BiP. Results: The synthesis, assembly, transpotation and expression of sB27 molecule were completed through the same pathway inside C1R cell line as cell surface B27 molecules although only part of the sB27 molecules finished the whole process. Most of the sB27 molecules were retained inside the endoplasmic reticulum. Conclusion: As a product of alternative splicing of B27 molecules, sB27 molecule which had been released to the supernatant had similar cell biology to its cell surface counterpart. It is speculated that most of the sB27 molecules retained inside endoplasmic reticulum would be degraded and presented to CD4⁺ T cells. through class Ⅱ molecules. This hypothesis explained the recent findings that B27 related spondyloarthropathies had HLA class Ⅱ antigen association clues such as CD4⁺ T cell activation.