Multiple activation markers, such as CD69, MKI67, CCL5, CTLA4, IFNG and GZMB, were found to be enriched in the NK cells of brucellosis patients, indicating the presence of an activated NK cell response as a distinctive feature for brucellosis patients, especially for those at the acute stage (Figure 6A, Figure S8A). Here, CD69 is linked to brucellosis.