Prevalence of KIR2DL2/DS2 and KIR2DL3 and presence of B19V in patients with thyroid disorders

Natural killer (NK) cells are crucial components of the innate immune system and provide a first line of defence against infection. NK cell function is controlled by a network of activating and inhibitory receptors, prominent among these are the killer cell immunoglobulin-like receptors (KIR), a family of genes clustered in one of the most variable regions of the human genome - on chromosome 19q13.4. This study aimed to investigate the possible interplay between KIR allotype, B19 infection and thyroid disorders. Thyroid gland tissue of 30 patients with autoimmune thyroid gland diseases (AITD) [median age 49 years (IQR: 37 – 59)], 30 patients with non-autoimmune thyroid gland diseases (non- AITD) [median age 53 years (IQR: 41 – 62)] and 30 randomly selected age and gender matched deceased subjects whose histories did not show any of autoimmune or thyroid diseases (control group) were enrolled in the study. The presence of B19V, KIR2DL2/DS2 and KIR2DL3 were detected using PCRs (nPCR, PCR). The results showed that 28% of thyroid tissue of AITD and 67% of non-AITD resulted positive for the presence of B19V, in contrast only 5% control tissue samples harboured B19V DNA. B19V positive AITD patients had increased frequency of KIR2DL2/DS2 homozygosity and decrease of the homozygous KIR2DL3 genotype compared to B19V negative ones (33% vs 21% and 17% vs 46%, respectively). Overall, although our data shows that B19V positive patients with AITD have increased frequency of the KIR2DL2/DS2 allele (both in homozygosity and heterozygosity condition), suggesting an impairment of NK cell function that might allow virus replication and pathogenic effect, further studies in a larger group of patients are however needed to characterize the contribution of B19V and KIR molecules in defining susceptibility to thyroid disease.