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 non-Hodgkin lymphoma.