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Objective: Previous studies have shown that human leukocyte antigen (HLA)‐B27 induces the accumulation of unfolded proteins in the endoplasmic reticulum (ER) to cause ER stress, resulting in the unfold protein response (UPR), apoptosis and autophagy. However, it is still unknown whether it affects the survival of monocytes. In this study, we attempted to examine the effect of HLA‐B27 gene knockout on the proliferation and apoptosis of THP‐1 monocytic cell line and its potential mechanism. Methods: HLA‐B27 gene knockout THP‐1 cell line was constructed by lentivirus infection, and knockout efficiency was detected by immunofluorescence, quantitative reverse transcription ‐ polymerase chain reaction (qRT‐PCR) and western blot. Cell Counting Kit‐8 (CCK‐8) method and Annexin‐V/PI double staining were used to detect the proliferation and apoptosis of the constructed THP‐1 cell line, respectively. qRT‐PCR was used to detect the effect of HLA‐B27 inhibition on the expressions of ER molecular chaperone binding immunoglobulin protein (BiP) and genes about the UPR pathway. The proliferation rate of human BiP protein‐stimulated THP‐1 cells was detected by CCK‐8 method. Results: HLA‐B27 gene knockout THP‐1 cells were successfully constructed by lentivirus infection. Knockout of HLA‐B27 effectively promoted the proliferation of THP‐1 cells and inhibited the apoptosis induced by cisplatin. qRT‐PCR showed that BiP was synchronously increased, while activation of UPR pathway was inhibited. Stimulation with human BiP promoted the proliferation of THP‐1 cells in a concentration‐dependent manner. Conclusions: HLA‐B27 inhibition can promote the proliferation and inhibit the apoptosis of THP‐1 cells. The inhibition function may be achieved through promotion of BiP and inhibition of UPR pathway activation. [ABSTRACT FROM AUTHOR]