Abstract: A process for removing immunosuppressive substances from the blood serum of cancer patients comprises contacting the serum at a temperature below room temperature and preferably not greater than 5.degree. C., with Protein A of S. aureus immobilized on a substrate. Conducting the immunoabsorption at low temperature reduces the amount of anaphylatoxins produced in the process and thereby reduces the side effects of immunoperfusion treatment. An apparatus for low-temperature immunoperfusion treatment comprises a chamber for containing the immunoabsorbent, inlet and outlet tubes connected to the chamber, and a cooling jacket surrounding the chamber and at least a portion of the inlet tube.