It is an inhibitory ligand for IL-2 on T cells, and binds all available IL-2 which prevents further T cell proliferation

It cleaves the intracellular ITAM motifs from the CD3 and ζ (zeta) chains of T cells, preventing intracellular signal transduction

It replaces the binding of CD28 to B7 (CD80 & CD86), and removes B7 (CD80 & CD86) from the dendritic cell surface

By binding the CTLA-4 receptor on T cells to induce apoptosis in these cells