Antibodies to phenolic glycolipid-I during long-term therapy: serial measurements in individual patients.

Levels of IgM antibody to phenolic glycolipid-I (PGL-I) were measured in serum specimens collected over the initial 5 or more years of therapy from 11 leprosy patients. All three patients with paucibacillary disease had undetectable levels of antibody throughout their treatment. The eight patients with multibacillary disease had initially elevated levels which fell quite rapidly with treatment, reaching levels of 10% to 30% of their initial pre-treatment level after 5 years of therapy. The single patient with prolonged therapeutic noncompliance had an increase in antibody level, although clinical or bacteriologic relapse was not documented. These results in individual patients demonstrate that IgM antibody to PGL-I declines rapidly and consistently with treatment in multibacillary patients.