They are wrong. > The appendix has been identified as an important component of mammalian mucosal immune function, particularly B cell-mediated immune response

They are wrong. > The appendix has been identified as an important component of mammalian mucosal immune function, particularly B cell-mediated immune responses and extrathymically derived T cells. https://en.wikipedia.org/wiki/Appendix_(anatomy)#Functions https://en.wikipedia.org/wiki/Appendix_(anatomy)#Functions