title: IgM and IgG antibodies to phenolic glycolipid I from Mycobacterium leprae in leprosy: insight into patient monitoring, erythema nodosum leprosum, and bacillary persistence.
abstract: Serum IgM and IgG antibodies against Mycobacterium leprae-derived phenolic glycolipid I (PG) were determined in leprosy patients, contacts, and controls by enzyme-linked immunosorbent assay (ELISA). Anti-PG IgM levels increased from the tuberculoid (TT) to the lepromatous (LL) pole of the disease spectrum. There was a positive linear correlation between anti-PG IgM and bacillary index (BI). Patients with erythema nodosum leprosum (ENL) had lower levels of serum anti-PG IgM than non-ENL patients of comparable BI, suggesting that anti-PG IgM is involved in the pathogenesis of ENL. Initial observations indicate that high anti-PG IgM levels in bacillary-negative patients might reflect bacillary persistence. A study of 2 different substrate reagents in the ELISA [2,2'-azino-di(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 0.1 mM H2O2, serum diluted 1:20, and o-phenylenediamine (OPD), 5 mM H2O2, serum diluted 1:300] showed generally good correlation in detection of anti-PG IgM. However the OPD system detected more paucibacillary disease (BT), while the ABTS system detected the significant effect of ENL on the relationship between BI and anti-PG IgM. Anti-PG IgM was clearly dominant over anti-PG IgG. However, certain patients, including several patients who had upgraded from LL and borderline lepromatous leprosy (BL), showed high levels of anti-PG IgG. Since studies have shown that LL patients are selectively deficient in cell-mediated immunity, T-cell products may be required for the IgM to IgG isotype switch. We conclude that anti-PG IgM is useful for monitoring the bacillary load in individual patients and should prove useful for leprosy control strategies.
mesh_terms: D000907:Antibodies, Bacterial / Q000032:analysis*; D000942:Antigens, Bacterial; D001666:Binding Sites, Antibody; D004797:Enzyme-Linked Immunosorbent Assay; D004893:Erythema Nodosum / Q000276:immunology* / Q000382:microbiology; D006017:Glycolipids / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis* / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000032:analysis* / Q000096:biosynthesis; D007918:Leprosy / Q000276:immunology* / Q000382:microbiology; D009166:Mycobacterium leprae / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D006017:Glycolipids; D007074:Immunoglobulin G; D007075:Immunoglobulin M; C045169:phenolic glycolipid I, Mycobacterium leprae