Serum soluble adhesion molecules in multiple sclerosis: raised sVCAM-1, sICAM-1 and sE-selectin in primary progressive disease

Leucocyte invasion into the central nervous system in multiple sclerosis (MS) is complex, involving T-cell/endothelium interaction dependent upon initial adhesion mediated by molecules such as E-selectin, L-selectin, intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Circulating levels of these can be measured by sensitive enzyme-linked immunoassay (ELISA) techniques. To assess whether serum concentrations of soluble adhesion molecules vary across the spectrum of patients with relapsing-remitting (RR), secondary progressive (SP) and primary progressive (PP) MS, we measured circulating levels of soluble (s)E-selectin, sl-selectin, sICAM-1 and sVCAM-1 in serum obtained from 78 PPMS patients, 71 patients with RRMS, 65 patients with SPMS and 66 patients with other neurological disease using commercially available ELISA systems. Levels of serum sVCAM-1 were significantly elevated in PPMS compared with RRMS in remission (P = 0.0001) and in relapse (P = 0.0001), whilst sICAM-1 was significantly elevated in PPMS compared with all other MS groups (vs SPMS, P = 0.006; vs RRMS in relapse, P = 0.003; vs RRMS in remission, P = 0.0001). Serum sE-selectin levels were significantly higher in PPMS compared with all other groups except inflammatory neurological disease (IND) [vs SPMS, P = 0.029; vs RRMS in relapse, P = 0.002; vs RRMS in remission, P = 0.001; vs non-inflammatory neurological disease (NIND), P = 0.002; vs IND, P = 0.076]. In PPMS there was no correlation between levels of any adhesion molecule and disability or disease duration. These results provide evidence for significant immunological heterogeneity in MS and suggest that different leucocyte/endothelial cell interactions may be active in various MS subgroups. It also challenges the hypothesis that PPMS is a less inflammatory form of the disease.