CTLA4 and B-cell chronic lymphocytic leukemia: This allowed us to select the corresponding receptor/ligand couples possibly involved in the NLC/CLL cell interaction: VCAM1, CD28, CD31 (PECAM-1 gene), LFA-1 (SELPLG gene), CD2, CD86, CTLA4, CD62 (SELP gene), LFA-3 (CD58 gene) (Supplementary Table 2).