CTLA-4 (CD152) is involved in T-lymphocyte co-stimulatory pathways modulati
ng both humoral and cellular immune response. The membrane-external domain
has been prepared and crystallized. The unit-cell parameters are a = b = 43
, c = 143 Angstrom with the symmetry of space group P3(1)21 or its enantiom
er and the crystals diffract to 2.7 Angstrom resolution at synchrotron beam
lines.