A method for purifying an immunosuppressant
protein (HISP) has the steps of obtaining supernatant from hNT cells; exposing the supernatant to preparative
polyacrylamide gel electrophoresis to produce 20 isoelectric fractions, including active isoelectric fraction #10; placing the active isoelectric fraction on a Blue
Sepharose column to bind
albumin; and collecting the free fraction containing the concentrated, isolated HISP. Also disclosed is a method of treating
inflammation, using an effective amount of an HISP. The HISP is anionic, has a molecular weight of 40-100 kDa, an
isoelectric point of about 4.8 and is obtained from the supernatant of hNT cells, but not from NCCIT embryonal
carcinoma cells, T98G
glioblastoma cells or THP-1 monocytic
leukemia cells. HISP can maintain T cells in a quiescent G0 / G1 state without lowering their viability. HISP loses activity when treated with heat, pH2, pH11, or mixed with
trypsin or
carboxypeptidase, but not with
neuraminidase. HISP can suppress proliferation of responder
peripheral blood mononuclear cells in allogeneic mixed
lymphocyte cultures; HISP can suppress T-
cell proliferation and IL-2 production in response to
phorbol 12-myristate 13-acetate (PMA), ionomycin and concanavalin-A. HISP does not bind to
heparin-
sepharose CL-B gel; or to
albumin-binding resin Blue
Sepharose. HISP is concentrated with YM10
ultrafiltration. HISP does not act through the T-
cell receptor-CD3 complex or via altered accessory
signal cells. A method of treating
inflammation comprises administering an effective amount of hNT neuronal cells.