By immunostaining of a variety of tissues, we and others have observed that whereas Mab to CD105 has a high affinity for angiogenic blood vessels (e.g. in tumours, stroke and psoriatic tissues), it often fails to react with the normal microvessels decorated by pan-endothelial markers, for example, CD31, vWF, CD34, PAL-E (Burrows et al, 1995; Kumar et al, 1996; Bodey et al, 1998; Miller et al, 1999; Brewer et al, 2000; Fonsatti et al, 2001 and our unpublished data). The gene discussed is PECAM1; the disease is Stroke.