Breakdown product of factor B as an index of complement activation in lepromatous leprosy and its relation with bacillary load

Genetic variants of complement genes ficolin-2, mannose-binding lectin and complement factor H are associated with leprosy in Han Chinese from Southwest China

The complement system plays multiple roles in host defense against infection and is supposed to confer genetic susceptibility to leprosy. We aimed to examine whether genetic variants of the Ficolin-2 (FCN2), Mannose-binding lectin (MBL2) and Complement factor H (CFH) genes, which are involved in activation and regulation of the complement system, are associated with leprosy in Han Chinese from Southwest China. 527 leprosy patients and 583 matched controls were recruited from Yunnan Province, China, and were analyzed in this study. We sequenced the promoter region of the FCN2 and MBL2 genes and exon 8 of the FCN2 gene and genotyped three tag SNPs of the CFH gene. Association analysis was performed to discern potential effect of these three genes with leprosy and its subtypes. Luciferase assay was used to characterize the role of different promoter alleles of the FCN2 and MBL2 genes. Genetic variants of FCN2 (rs3811140 and rs7851696), MBL2 (rs11003125, rs7100749, rs11003124 and rs7096206) and CFH (rs1065489 and rs3753395) were significantly associated with leprosy and its subtypes. Haplotypes/genotypes representing low FCN2 and MBL2 transcriptional activity conferred risk to paucibacillary leprosy. Our data confirmed the expected positive association of complement genes with leprosy susceptibility and clinical outcomes in Han Chinese.

Lucio's phenomenon/erythema necroticans

Lucio's phenomenon/erythema necroticans is a peculiar reaction pattern that occurs in untreated pure primitive diffuse lepromatous leprosy (PPDL) and/or relapsing leprosy recognized as spotted leprosy of Lucio. The small number of reported cases in the world literature suggests that it is fairly uncommon. Its clinical features are fairly characteristic and consist of extensive, bizarre, painful ulcerations of the skin, with constitutional symptoms being conspicuous by their absence. The clinical diagnosis is confirmed by microscopic pathology marked by proliferation and mobilization of polyblasts and histiocytes, dilatation, endothelial proliferation, luminal occlusion, and thrombosis of the superficial and mid-dermal blood vessels and demonstration of acid-fast bacilli in the blood vessel walls. Its precise pathogenesis is still unclear, but is believed to occur either through the usual or the alternate pathway of complement activation in the natural history of erythema nodosum leprosum. The clinical and immunological features of reactions in leprosy, including erythema nodosum leprosum, are well known and have been critically evaluated elsewhere.

Comprehensive evaluation of complement components in the course of type I (Lepra) and type II (ENL) reactions

Complement components C1q and C4 of classic pathway; C3d, a breakdown product of C3, and factor B of alternate pathway: and C3, a component both of classic and alternate pathways, were studied in 35 patients, comprising 18 type I (Lepra) and 17 type II (ENL) reactions. There was a significant decrease in C3 and factor B with a concomitant rise of C3d during ENL. These changes indicate their preeminent role in immunogenesis of type II (ENL) reaction. The changes in the classic pathway components, on the other hand, were insignificant, apparently suggesting its limited involvement in ENL. Furthermore, reversion of factor B and C3d after subsidence of reaction is intriguing and may indicate that they are not substantially affected even with contemporary treatment. Complement components, of both classic and alternate pathways, showed no significant alterations either during type I (Lepra) reaction or after its amelioration.