The results showed that three cytokines, including the Fas receptor (Fas), platelet factor 4 (PF4) and interleukin-22 (IL-22), were significantly upregulated in WSSV-infected shrimp at 6 h post-infection compared with the control (PBS) (Fig 1B), suggesting that these cytokines might play positive regulatory roles in the shrimp immune response against the WSSV infection. Here, PF4 is linked to infection.