In this retrospective multicentre study we reviewed data of 255 patients with psoriasis genotyped for HLA-C*06 who started ustekinumab treatment between January 2014 and March 2015.
We concluded that psoriasis is based on a melanocyte-specific immune response and that HLA-C*06:02 may predispose to psoriasis via this newly identified autoimmune pathway.
Among cases of psoriasis, it was noted that there was a significant association of HLA-C*06 positivity with female psoriatics [p = 0.006; OR 2.49 (1.28-4.87)] and early age of onset of psoriasis [p = 0.002; OR 2.04 (1.29-3.20)].
We further identified multiple independent new susceptibility loci in HLA-C, HLA-B, HLA-DPB1 and BTNL2 and an intergenic variant, rs118179173, associated with psoriasis and confirmed the well-established risk allele HLA-C*06:02.
We first demonstrate hypermethylation of HLA-C gene in psoriatic epidermis, suggesting that HLA-C hypermethylation may be an epigenetic marker in psoriasis.
In this retrospective study, both HLA-C*06:02-positive and -negative patients demonstrated good responses to ustekinumab (86% vs. 76%, respectively, achieved at least a 75% improvement from baseline in Psoriasis Area and Severity Index [PASI 75] at week 24).
Moreover, we need to determine allele-specific effects of ERAP1 variants in the context of HLA-B*51 and HLA-Cw*6, which are associated with Behçet's disease and psoriasis, respectively.
Of note, these 'MHC-I-opathies' show a differential immunopathology, probably reflecting antigenic differences within target tissues: HLA-B(*)51 is linked to ocular and mucocutaneous disease but not gut involvement, and HLA-C(*)0602 is linked to type I psoriasis but not scalp or nail disease.
Among identified psoriasis risk variants, three were more strongly associated with PsC than PsA (rs12189871 near HLA-C, p = 5.0 × 10(-19); rs4908742 near TNFRSF9, p = 0.00020; rs10888503 near LCE3A, p = 0.0014), and two were more strongly associated with PsA than PsC (rs12044149 near IL23R, p = 0.00018; rs9321623 near TNFAIP3, p = 0.00022).
Strong additive effects when combining HLA-C*06 with IL23A, IL23R, IL12B, NFKB1 or TNIP1 were restricted to the severe cohort, indicating that activation of these pathways may influence disease severity in psoriasis.
Moreover, genetic interaction between LCE3C_LCE3B-del and HLA-C*06, located in the psoriasis susceptibility regions 4 and 1 (PSORS4 and 1), has been reported in several populations.
Deletion mapping using microsatellite haplotyping, CGH array and PCR analysis established that the genomic deletion spanned 49-72 kb between HCG22 and TCF19, removing CDSN as well as five other genes within the psoriasis susceptibility region 1 (PSORS1) on 6p21.33.
We genotyped 142 patients and 160 healthy volunteers to evaluate the possible relationship between susceptibility to psoriasis and the HLA-C*0602 allele and polymorphisms in the TNF, IL12B, and IL23R genes.
In patients with PsA expressing the HLA-C*06 antigen, the latency between the onset of psoriasis and onset of joint symptoms is longer than in those without this marker.
The low-expressing HLA-E*01:01 allele was associated with psoriasis (P = 0.0018), although this association was dependent on HLA-C. Our findings support a potential immunoregulatory role for NK cells in psoriasis and suggest the importance of future studies to investigate the contribution of NK cells and their regulatory receptors to the pathogenesis of psoriasis.
Previously, the authors observed an association with HLA-C×06 in psoriasis (PS) and benign migratory glossitis (BMG); however, HLA-C was not surveyed in FT.