Fluorescence-activated cell sorting (FACS) staining with CD48 antibodies showed 721.221, a human B-lymphoblastoid cell line, BCBL1, a B cell lymphoma cell line, RAJI, a lymphoblast cell line, and RPMI 8866, a B-lymphoid cell line, as cells positive for CD48 expression, Jurkat, a T-lymphoid cell line, and BJAB, a lymphoma cell line, as slightly positive, and K562, a lymphoblast cell line, as CD48-negative cell line (Figure 1B). Here, CD48 is linked to lymphoma.