Table 1. Frequencies (number of individuals that carry an alleles/total number of individuals) of 21 blue tit MHC-I alleles.
| MHC allele | Frequency |
| 220 | 0.005 |
| 232 | 0.002 |
| 235 | 0.132 |
| 238 | 0.338 |
| 240 | 0.173 |
| 242 | 0.757 |
| 243 | 0.168 |
| 245 | 0.165 |
| 247 | 0.047 |
| 250 | 0.019 |
| 253 | 0.050 |
| 256 | 0.123 |
| 259 | 0.265 |
| 262 | 0.468 |
| 265 | 0.128 |
| 267 | 0.087 |
| 270 | 0.012 |
| 273 | 0.012 |
| 276 | 0.097 |
| 279 | 0.768 |
| 282 | 0.035 |
421 individuals were screened for MHC genotype and 17 MHC alleles that occurred in more than five individuals were included in statistical analyses for infection status (bold). Allele 250 was excluded from the analysis on infection intensity since it only was found in three infected individuals.