Differential gene expression levels might explain association of LAIR2 polymorphisms with pemphigus.

The leukocyte-associated immunoglobulin-like receptor 1 (LAIR-1) is a collagen-binding inhibitory receptor important for the regulation of immune responses, expressed on the majority of peripheral blood mononuclear cells (PBMC). LAIR-2 is a soluble homolog that antagonizes LAIR-1 inhibitory function by binding the same ligands. We sought to investigate whether LAIR1 and LAIR2 single nucleotide polymorphisms (SNP) are associated with differential mRNA expression levels. We analyzed 14 SNPs of LAIR1 (6) and LAIR2 (8) by mass spectrometry-based genotyping and extracted mRNA from PBMC of 177 healthy subjects, followed by quantitative assays. Four SNPs of LAIR1 and two SNPs of LAIR2 mark differential mRNA levels in healthy individuals. To verify the biological relevance of these findings, we analyzed additional 515 individuals (282 patients and 233 controls) to check if LAIR1 and LAIR2 differential mRNA expression could be related to susceptibility to pemphigus foliaceus (PF), an autoimmune blistering skin disease endemic in Brazil. Two LAIR1 variants (rs56802430 G, OR = 1.52, p = 0.0329; rs11084332 C, OR = 0.57, p = 0.0022) and one LAIR2 (rs2287828 T+, OR = 1.9, p = 0.0097) contribute to differential susceptibility to PF. Furthermore, we demonstrate interactions among four LAIR2 SNPs (rs2042287, rs2287828, rs2277974 and rs114834145). A haplotype harboring these SNPs is strongly associated with higher LAIR2 mRNA levels (4.5-fold, p = 0.0069) and with higher susceptibility to PF (OR = 4.02, p = 0.0008). We suggest that LAIR1 and LAIR2 genetic variants are associated with regulation of gene expression and variable PF susceptibility, and show indirect association of LAIR2 differential mRNA expression with PF pathogenesis. Our data demonstrate how this relatively unknown disease can add invaluable knowledge regarding the role of LAIR1 and LAIR2 in immune responses.