FCRL4 and HIV infectious disease: As FcRL4 has been implicated in TGF-β1 mediated suppression of B cell function in HIV infection[43] and RNA-Seq analysis suggested that TGF-β3 also induces the expression of FcRL4 (Fig 5B), we hypothesized that FcRL4 might also be involved in the inhibition of Syk phosphorylation by TGF-β3.