(A–C), flow cytometric analysis of peripheral blood lymphocytes from transgenic mice for expression of human CD55, thrombomodulin (TBM) and CD39. Thin line, mouse transgenic for 3-gene construct #2 (H-2Kb/CD55-TBMCD39); thick line, mouse transgenic for 4-gene construct #3 (H-2Kb/CD55- TBM-CTLA4Ig-CD39); filled line, non-transgenic littermates. (D) detection of CTLA4-Ig in serum by incubation with COS-7 cells transiently transfected with baboon CD86. Key as above.