CD19 and neoplasm: We have previously demonstrated these in vivo activated B cells express CD19, B220, CD23, HEL+ with subtle upregulation of MHC-II and CD95.4,5 Importantly, no proliferation is observed when naïve 5C.C7 CD4 T cells are transferred into I-E- anti-CD40 activated SWHEL transgenic tumour bearing mice (Figure S1f).