In lymphoid malignancies, CD40 is present on B-cell precursor acute lymphoblastic leukaemia (ALL (Uckun et al, 1990)), non-Hodgkin's lymphoma (NHL (Uckun et al, 1990)), Hodgkin's lymphoma (HL (O'Grady et al, 1994)) and multiple myeloma (MM (Westendorf et al, 1994)). This evidence concerns the gene CD40 and acute lymphoblastic leukemia.