Effect of cladribine treatment on beta-2 microglobulin and soluble intercellular adhesion molecule 1 (ICAM-1) in patients with multiple sclerosis.

β-2 Microglobulin ( β2M) is a low molecular weight protein located extracellularly and associated with class 1 antigens of the major histocompatibility complex and is considered a marker for disease activity in immune disorders. Cladribine (2-chloro-2-deoxyadenosine, 2-CDA) is a potent lymphocytotoxic agent under investigation in the treatment in MS patients. As β2M levels may indicate inflammatory events in CNS we determined CSF- β2M and serum β2M levels in patients with relapsing-remitting MS before and after cladribine treatment as well as in a control group. There was a significant β2M decrease in sera but not in CSF in MS patients after the cladribine treatment, associated with a slight but significant clinical improvement measured by Kurtzke's Expanded Disability Status Scale. We also found a significant decrease in sICAM-1 level in CSF but not in sera in MS patients. The data support a role of cladribine in MS therapy and deliver new information on cladribine immunological effects in MS patients.