Table 2. KIR genes and genotype frequencies compared between patients and the population group.
| Population group (400) | COVID-19 patients (396) | P value | OR (95% CI) | Pc* | |
|---|---|---|---|---|---|
| n (%) | n (%) | ||||
| Inhibitory KIR genes | |||||
| 2DL1 | 381 (0.953) | 393 (0.992) | 0.001 | 6.5 (1.9–34.7) | 0.011 |
| 2DL2 | 232 (0.580) | 249 (0.629) | 0.17 | 1.2 (0.9–1.6) | 1 |
| 2DL3 | 343 (0.858) | 372 (0.939) | 0.0002 | 2.6 (1.5–4.4) | 0.0022 |
| 2DL4 | 400 (1.00) | 396 (1.00) | |||
| 2DL5 | 223 (0.558) | 231 (0.583) | 0.48 | 1.1 (0.8–1.5) | 1 |
| 3DL1 | 373 (0.933) | 369 (0.932) | 1 | 1.0 (0.5–1.8) | 1 |
| 3DL2 | 400 (1.00) | 396 (1.00) | |||
| 3DL3 | 400 (1.00) | 396 (1.00) | |||
| Activating KIR genes | |||||
| 2DS1 | 155 (0.388) | 175 (0.442) | 0.13 | 1.3 (0.9–1.7) | 1 |
| 2DS2 | 231 (0.578) | 244 (0.616) | 0.28 | 1.2 (0.9–1.6) | 1 |
| 2DS3 | 145 (0.363) | 147 (0.371) | 0.82 | 1.0 (0.8–1.4) | 1 |
| 2DS4 | 376 (0.940) | 378 (0.955) | 0.43 | 1.3 (0.7–2.7) | 1 |
| - 2DS4 DV+ | 334 (0.835) | 324 (0.818) | 0.58 | 0.9 (0.6–1.3) | 1 |
| - 2DS4 FL+ | 125 (0.313) | 123 (0.311) | 1 | 1.0 (0.7–1.4) | 1 |
| 2DS5 | 127 (0.318) | 144 (0.364) | 0.18 | 1.2 (0.9–1.7) | 1 |
| 3DS1 | 148 (0.370) | 165 (0.417) | 0.19 | 1.2 (0.9–1.6) | 1 |
| Genotypes | |||||
| A/A | 115 (0.288) | 111 (0.280) | 0.87 | 0.97 (0.7–1.3) | 1 |
| - 2DS4 DV/DV | 72 (0.180) | 69 (0.174) | 0.85 | 0.96 (0.7–1.4) | 1 |
| - 2DS4 DV/FL and FL/FL | 43 (0.108) | 42 (0.106) | 1 | 0.99 (0.6–1.5) | 1 |
| B/x | 285 (0.713) | 285 (0.720) | 0.87 | 1.0 (0.8–1.4) | 1 |
| Centromeric KIR motifs | |||||
| cA01/cA01 | 169 (0.423) | 144 (0.364) | 0.09 | 0.8 (0.6–1.0) | 1 |
| cA01/cB01, cA01/cB02 | 176 (0.440) | 228 (0.575) | 0.0001 | 1.7 (1.3–2.3) | 0.0003 |
| cB01/cB01, cB01/cB02, cB02/cB02 | 55 (0.138) | 24 (0.061) | 0.0003 | 0.4 (0.2–0.7) | 0.0009 |
| Telomeric KIR motifs | |||||
| tA01/tA01 | 237 (0.592) | 207 (0.523) | 0.05 | 0.7 (0.6–1.0) | 0.16 |
| tA01/tB01 | 139 (0.348) | 156 (0.394) | 0.19 | 1.2 (0.9–1.6) | 0.56 |
| tB01/tB01 | 24 (0.060) | 33 (0.083) | 0.22 | 1.4 (0.8–2.6) | 0.65 |
*P values were calculated for comparisons between Sardinian COVID-19 patients and the population group. Pc corresponds to P values corrected for multiple comparisons.
Abbreviations: OR = odds ratio; CI = confidence interval; B/x = KIR haplotypes AB and BB; 2DS4 DV+ = deletion variant alleles of the KIR2DS4 gene; 2DS4 DV/DV = homozygous for deletion variant alleles of the KIR2DS4 gene; 2DS4 DV/FL and FL/FL = heterozygous and homozygous for full-length allele variants of the KIR2DS4 gene. Group A and B KIR haplotypes have distinctive centromeric and telomeric KIR gene-content motifs as described by Pyo CW et al. [56]. No cB03 motifs were found in COVID-19 patients or the population group.