CD30 ligand (CD30L) and CD30 are interacting cellsurface glycoproteins that are members of the tumour necrosis factor (TNF) and tumour necrosis factor receptor (TNFR) superfamilies. In humans, CD30L is expressed at high levels on activated T cells. There is conflicting evidence with regard to cell surface expression of CD30L on primary human B cells. An initial report of constitutive CD30L expression on peripheral blood B cells33 has not been substantiated.