ROR1 and neoplasm: ROR1RCD28+ T cells stained brightly for IFNγ when co-cultured with ROR1+ tumor targets EL4-ROR1, Kasumi-2, and CLL cells, but did not produce IFNγ, as evidenced by similar staining of unchallenged cultures (mock; media only) to co-cultures with ROR1neg cells from EBV-transformed healthy donor B-cell lymphoblastoid cell lines (LCL), NALM-6, and parental EL4 cells (Fig 4a top).