“…4,18 They are further methylated and converted to trimethyl arsenic compounds, including AsCho, in marine animals. 5,6 It was reported that AsCho had a weak, but significant, in vivo acute toxicity in mice, 7 but we recently demonstrated that AsCho had no in vitro cytolethality on cultured mouse splenocytes, thymocytes, Peyer's patch lymphocytes, macrophages and bone marrow cells. 1,8,9 In this study, we examined whether AsCho has any in vivo immunotoxicity, and found that it was slightly, but significantly, immunotoxic in vivo.…”