Increased frequencies of activating natural killer receptors are associated with liver injury in individuals who do not eliminate hepatitis C virus

This study was designed to investigate the role of killer immunoglobulin-like receptor (KIR) genes in the outcome of hepatitis C virus (HCV) infection. In patients who cleared the virus (HCV RNA-) we found a decrease of 2DL2 (P= 0.04), and 2DS2 (P= 0.014) accompanied by an increase of 2DS5 (P= 0.04). Those RNA+ patients with elevated levels of hepatic transaminases (HCV RNA+ elevated alanine aminotransferase) showed an increased frequency of 2DS3 (P= 0.018). Additionally, in cirrhotic patients we found an increased frequency of individuals having two copies of 3DS1 and HLA-Bw4 (P= 0.016). We conclude that higher natural killer cytotoxicity might be associated with a worse progression of the HCV infection.

KIR genes polymorphism in Argentinean Caucasoid and Amerindian populations

In natural killer cells, killer immunoglobulin-like receptors (KIRs) loci code for either inhibitory or activating receptors, and according to the number of genes present in each individual, it is possible to identify a high rate of polymorphism in the populations. We performed KIR typing by polymerase chain reaction-sequence-specific oligonucleotide probing in 402 Argentinean Caucasoid and in two Amerindian populations (101 Wichis and 54 Chiriguanos) from the North of Argentina. KIR2DL4, KIR3DL2, KIR3DL3 and KIR3DP1 were always present, whereas the frequencies of KIR2DL1, KIR2DL3, KIR2DS4, KIR3DL1 and KIR2DP1 ranged between 84% and 96%. The frequencies of KIR2DS2, KIR2DL2, KIR2DL5, KIR2DS5, KIR2DS1 and KIR3DS1 ranged between 41% and 62%. The KIR2DS3 with a frequency of 29% in Argentinean Caucasoid population was present at a very low frequency in Amerindian populations. Haplotype segregation studies performed in 10 Wichi families showed the presence of only three haplotypes: A, B5 and B1. The Amerindian populations showed several similarities to Asian but not to Caucasoid populations with regard to the frequency of KIR2DS3, full-length KIR2DS4 gene and KIR2DL4 alleles.

KIR receptors and HLA-C in the maintenance of pregnancy

The present study demonstrated that patients who have recurrent spontaneous abortions (RSA) presented a decreased number of killer immunoglobulin-like inhibitory receptors (KIR), in particular KIR2DL2. The KIR AA genotype was found increased in comparison with controls. Individuals AA will also be homozygous for 2DL3, which in contrast to 2DL2, show a weaker interaction with C1 ligands and therefore a weaker inhibition. The present study might support that in RSA patients, the balance between inhibitory and activating receptors present in natural killer cells is inclined toward an activating state that may contribute to pregnancy loss.