Basiliximab functions as an IL-2 receptor antagonist by binding with high affinity to the alpha chain of the high affinity IL-2 receptor complex and inhibiting IL-2 binding. Basiliximab is specifically targeted against IL-2Ralpha, which is selectively expressed on the surface of activated T-lymphocytes. This specific high affinity binding of basiliximab to IL-2Ralpha competitively inhibits IL-2-mediated activation of lymphocytes, a critical pathway in the cellular immune response involved in allograft rejection.