Cell-mediated immune response to copolymer I in multiple sclerosis measured by the macrophage procoagulant activity assay.

The macrophage/monocyte procoagulant activity (MPCA) assay, a sensitive and specific in vitro test for cell-mediated immunity, has been used to ascertain the reactivity of MS peripheral blood mononuclear cells (PBM) to copolymer I (Copl), a synthetic peptide analogue of myelin basic protein (MBP) currently being tested as a possible therapeutic agent in multiple sclerosis (MS). Because the suppressive effect of Copl is believed to lie in its possible cross-reactivity with MBP, the reactivity of PBM of MS patients to MBP was also tested. MS patients either at the stable phase of the relapsing/remitting form or with chronic progressive disease were investigated and compared with patients with other diseases and with healthy subjects. The reactivity to Copl was significantly increased in patients with chronic progressive disease but not in stable MS patients or in control subjects. No difference in reactivity to MBP between MS patients and healthy subjects was found regardless of disease status. However, in the control group comprising patients with other diseases, MBP reactivity was significantly elevated. In chronic progressive MS patients, a relationship was found between the response to Copl and that to MBP, supporting the possibility of an immunological cross-reactivity between these two antigens. There was no significant difference in reactivity to the non-specific stimulant, lipopolysaccharide, between the MS and control groups.