Polymorphisms of HLA microsatellite marker in Tunisian pemphigus foliaceus

Pemphigus foliaceus (PF) is an autoimmune blistering skin disease that partly results from genetic factors, especially from human leucocyte antigen (HLA) class II genes. Several data have reported the involvement of microsatellite (STR) markers across different regions of the HLA in many auto-immune diseases. To test the hypothesis of the existence of a major HLA haplotype predisposing to PF, we analyzed six polymorphisms of microsatellite loci at 6p21.3-21.4 spanning HLA: D6S291, D6S273, TNFa, MICA, D6S265 and D6S276 in 81 PF patients compared to 123 healthy individuals recruited from the south of Tunisia. In this study, after Bonferroni's correction, 3 STR alleles from the TNFa locus were associated with the disease: the allele TNFa(∗)2 (p(c) = 4.2×10(-6)) and, at a lower level, the TNFa(∗)5 (p(c) = 0.014) as susceptibility alleles and TNFa(∗)6 (p(c) = 0.014) as protective ones. Furthermore, the expression of the TNFa(∗)2/TNFa(∗)5 genotype seem to confer susceptibility to PF (p = 0.00001, OR = 11.25). Interestingly, no significant LD was found between TNFa2/TNFa5 alleles and DRB1(∗)03/DRB1(∗)04 alleles. However, the multivariant regression analysis indicates that both the HLA class II and the TNFa alleles remained significant (p < 0.001). Although, these findings rejected our hypothesis on the existence of HLA susceptibility haplotype, they assessed the role of TNFa loci. Accordingly, TNFa seem to contribute to the aethiopathogenesis of Tunisian endemic PF may be by the induction of a high TNFα production which is known to enhance the autoimmune cascade of the disease.