Table 1.
The Tezenas du Montcel classification system of the HLA-DRB1 shared epitope in RA.*
| Amino Acid Residue | ||||||
|---|---|---|---|---|---|---|
|
|
||||||
| HLA-DRB1 Alleles | 70 | 71 | 72 | 73 | 74 | Classification |
| Susceptibility alleles | ||||||
| 0401, 1303† | K | R | A | A | S2 | |
| 0101, 0102, 0404, 0405, 0408, 10, 1402†, 1406† | Q/R | R | R | A | A | S3P |
| Low-risk alleles | ||||||
| 1501, 1502, 1503 | A | R | A | A | L (S1A) | |
| 0103, 0402, 1301, 1302 | E | R | A | A | L (S1E) | |
| 1102†, 1103†, 1202†, 1305†, 16 | D | R | R | A | A | L (S3D) |
| Nonsusceptibility alleles | ||||||
| 03 | Q | K | R | G | R | X |
| 0403, 0406, 0407 | Q | R | R | A | A | X |
| 07 | D | R | R | G | Q | X |
| 08 (except 0803) | D | R | R | A | L | X |
| 09 | R | R | R | A | E | X |
| 14 (except 1402 and 1406) | R | R | R | A | E | X |
In this system described by Tezenas du Montcel et al, alleles are divided into susceptibility (S) and nonsusceptibility (X) alleles according to the presence or absence of the amino acid sequence RAA at amino acid positions 72–74 (see Table 1 in ref. 8). The S alleles are then further subdivided according to the amino acid at position 71 (for S1, ARAA [S1A] or ERAA [S1E]; for S2, KRAA; and for S3, RRAA). The S3 alleles are then subdivided further according to the amino acid at position 70 (for S3D, DRRAA, and for S3P, QRRAA or RRRAA). In the analysis by Morgan et al (7), the S1A, S1E, S3D, and X alleles were pooled and classified as low-risk (L) alleles.
Allele is rare in Caucasians.
Letters represent the single-letter abbreviation for amino acids: K - lysine; R - arginine; A - alanine; Q - glutamic acid; G - glycine; D – aspartic acid; L – leucine; I – isoleucine.