However, in a study using BALB/c mice infected with L. sigmodontis, NK cells (identified as Dx5+CD3-) expanded significantly from 35 days post infection in the pleural cavity and down-regulated the inhibitory receptors Ly6C, Ly6A and Ly6G2, suggesting they are functioning here as effector cells rather than immunoregulators (28). This evidence concerns the gene LY6S and infection.