In addition, we also found that the number of TLR4<sup>+</sup>MDSCs and PD-L1<sup>+</sup>MDSCs increased in model mice with chronic brucellosis.<h4>Conclusion</h4>These findings expand the current understanding of persistent Brucella infection, and highlight that TLR4<sup>+</sup> and PD-L1<sup>+</sup> MDSCs hold potential as candidate biomarkers for assessing the severity and progression of brucellosis. The gene discussed is CD274; the disease is brucellosis.