CTLA4 and brucellosis: However, Brucella infection can undermine the protective immune response, resulting in the increased circulation of regulatory T-cells (Tregs) within the patient’s body, and the expression of CTLA4, a significant immune checkpoint for Tregs, is markedly elevated in individuals with chronic brucellosis, suggesting that Brucella may induce the overexpression of immune checkpoints in Tregs, potentially leading to the impaired control of Brucella infection [28].