Draft status: This content is under review, and may be subject to revision.

XX codes represent all HLA alleles within an allele group. They resemble NMDP multiple-allele code designations with an allele code of “XX”, e.g. HLA-A*01:XX. However, they differ from NMDP multiple-allele codes in the way the set of HLA alleles represented by an XX code may vary depending on the IPD-IMGT/HLA release version in use.

XX codes can be useful for transporting old HLA typing results to newer versions of the IPD-IMGT/HLA nomenclature, especially in cases where the original interpretation was based on a closed-world assumption using an outdated nomenclature version.

The MAC Service UI, maintained by the Be the Match® registry, has the ability to decode and expand XX codes.

https://hml.nmdp.org/MacUI/

HLA typing results described by XX codes tend to be highly ambiguous. For example, under IPD-IMGT/HLA release 3.33.0, the XX code HLA-A*01:XX represents the following set of 259 protein-level HLA types.

HLA-A*01:01
HLA-A*01:02
HLA-A*01:03
HLA-A*01:04
HLA-A*01:06
HLA-A*01:07
HLA-A*01:08
HLA-A*01:09
HLA-A*01:10
HLA-A*01:11N
HLA-A*01:12
HLA-A*01:13
HLA-A*01:14
HLA-A*01:15N
HLA-A*01:16N
HLA-A*01:17
HLA-A*01:18N
HLA-A*01:19
HLA-A*01:20
HLA-A*01:21
HLA-A*01:22N
HLA-A*01:23
HLA-A*01:24
HLA-A*01:25
HLA-A*01:26
HLA-A*01:27N
HLA-A*01:28
HLA-A*01:29
HLA-A*01:30
HLA-A*01:31N
HLA-A*01:32
HLA-A*01:33
HLA-A*01:35
HLA-A*01:36
HLA-A*01:37
HLA-A*01:38
HLA-A*01:39
HLA-A*01:40
HLA-A*01:41
HLA-A*01:42
HLA-A*01:43
HLA-A*01:44
HLA-A*01:45
HLA-A*01:46
HLA-A*01:47
HLA-A*01:48
HLA-A*01:49
HLA-A*01:50
HLA-A*01:51
HLA-A*01:52
HLA-A*01:53N
HLA-A*01:54
HLA-A*01:55
HLA-A*01:56N
HLA-A*01:57N
HLA-A*01:58
HLA-A*01:59
HLA-A*01:60
HLA-A*01:61
HLA-A*01:62
HLA-A*01:63
HLA-A*01:64
HLA-A*01:65
HLA-A*01:66
HLA-A*01:67
HLA-A*01:68
HLA-A*01:69
HLA-A*01:70
HLA-A*01:71
HLA-A*01:72
HLA-A*01:73
HLA-A*01:74
HLA-A*01:75
HLA-A*01:76
HLA-A*01:77
HLA-A*01:78
HLA-A*01:79
HLA-A*01:80
HLA-A*01:81
HLA-A*01:82
HLA-A*01:83
HLA-A*01:84
HLA-A*01:85
HLA-A*01:86
HLA-A*01:87N
HLA-A*01:88
HLA-A*01:89
HLA-A*01:90
HLA-A*01:91
HLA-A*01:92
HLA-A*01:93
HLA-A*01:94
HLA-A*01:95
HLA-A*01:96
HLA-A*01:97
HLA-A*01:98
HLA-A*01:99
HLA-A*01:100
HLA-A*01:101
HLA-A*01:102
HLA-A*01:103
HLA-A*01:104
HLA-A*01:105
HLA-A*01:106
HLA-A*01:107
HLA-A*01:108
HLA-A*01:109
HLA-A*01:110
HLA-A*01:111
HLA-A*01:112
HLA-A*01:113
HLA-A*01:114
HLA-A*01:115
HLA-A*01:116
HLA-A*01:117
HLA-A*01:118
HLA-A*01:119
HLA-A*01:120
HLA-A*01:121
HLA-A*01:122
HLA-A*01:123N
HLA-A*01:124
HLA-A*01:125
HLA-A*01:126
HLA-A*01:127
HLA-A*01:128
HLA-A*01:129
HLA-A*01:130
HLA-A*01:131
HLA-A*01:132
HLA-A*01:133
HLA-A*01:134
HLA-A*01:135
HLA-A*01:136
HLA-A*01:137
HLA-A*01:138
HLA-A*01:139
HLA-A*01:140
HLA-A*01:141
HLA-A*01:142
HLA-A*01:143
HLA-A*01:144
HLA-A*01:145
HLA-A*01:146
HLA-A*01:147Q
HLA-A*01:148
HLA-A*01:149
HLA-A*01:150
HLA-A*01:151
HLA-A*01:152
HLA-A*01:153
HLA-A*01:154
HLA-A*01:155
HLA-A*01:156
HLA-A*01:157
HLA-A*01:158
HLA-A*01:159
HLA-A*01:160N
HLA-A*01:161
HLA-A*01:162N
HLA-A*01:163
HLA-A*01:164
HLA-A*01:165
HLA-A*01:166
HLA-A*01:167
HLA-A*01:168
HLA-A*01:169
HLA-A*01:170
HLA-A*01:171
HLA-A*01:172
HLA-A*01:173
HLA-A*01:174
HLA-A*01:175
HLA-A*01:176
HLA-A*01:177
HLA-A*01:178N
HLA-A*01:179N
HLA-A*01:180
HLA-A*01:181
HLA-A*01:182
HLA-A*01:183
HLA-A*01:184
HLA-A*01:185
HLA-A*01:186N
HLA-A*01:187
HLA-A*01:188
HLA-A*01:189
HLA-A*01:190
HLA-A*01:191
HLA-A*01:192
HLA-A*01:193
HLA-A*01:194
HLA-A*01:195
HLA-A*01:196
HLA-A*01:197
HLA-A*01:198
HLA-A*01:199
HLA-A*01:200
HLA-A*01:201
HLA-A*01:202
HLA-A*01:203
HLA-A*01:204
HLA-A*01:205
HLA-A*01:206
HLA-A*01:207
HLA-A*01:208Q
HLA-A*01:209
HLA-A*01:210
HLA-A*01:211
HLA-A*01:212
HLA-A*01:213
HLA-A*01:214
HLA-A*01:215
HLA-A*01:216
HLA-A*01:217
HLA-A*01:218
HLA-A*01:219
HLA-A*01:220
HLA-A*01:221
HLA-A*01:222
HLA-A*01:223
HLA-A*01:224
HLA-A*01:225
HLA-A*01:226
HLA-A*01:227
HLA-A*01:228Q
HLA-A*01:229
HLA-A*01:230
HLA-A*01:231
HLA-A*01:232
HLA-A*01:233
HLA-A*01:234
HLA-A*01:235
HLA-A*01:236
HLA-A*01:237
HLA-A*01:238
HLA-A*01:239
HLA-A*01:240N
HLA-A*01:241
HLA-A*01:242
HLA-A*01:243
HLA-A*01:244
HLA-A*01:245
HLA-A*01:246
HLA-A*01:247N
HLA-A*01:248Q
HLA-A*01:249
HLA-A*01:250N
HLA-A*01:251
HLA-A*01:252
HLA-A*01:253
HLA-A*01:254
HLA-A*01:255
HLA-A*01:256
HLA-A*01:257
HLA-A*01:258N
HLA-A*01:259
HLA-A*01:260
HLA-A*01:261

Within the same IPD-IMGT/HLA release, the protein-level HLA types listed above correspond to the following set of 374 HLA alleles.

HLA-A*01:01:01:01
HLA-A*01:01:01:02N
HLA-A*01:01:01:03
HLA-A*01:01:01:04
HLA-A*01:01:01:05
HLA-A*01:01:01:06
HLA-A*01:01:01:07
HLA-A*01:01:01:08
HLA-A*01:01:01:09
HLA-A*01:01:01:10
HLA-A*01:01:01:11
HLA-A*01:01:01:12
HLA-A*01:01:01:13
HLA-A*01:01:01:14
HLA-A*01:01:01:15
HLA-A*01:01:01:16
HLA-A*01:01:01:17
HLA-A*01:01:01:18
HLA-A*01:01:02
HLA-A*01:01:03
HLA-A*01:01:04
HLA-A*01:01:05
HLA-A*01:01:06
HLA-A*01:01:07
HLA-A*01:01:08
HLA-A*01:01:09
HLA-A*01:01:10
HLA-A*01:01:11
HLA-A*01:01:12
HLA-A*01:01:13
HLA-A*01:01:14
HLA-A*01:01:15
HLA-A*01:01:16
HLA-A*01:01:17
HLA-A*01:01:18
HLA-A*01:01:19
HLA-A*01:01:20
HLA-A*01:01:21
HLA-A*01:01:22
HLA-A*01:01:23
HLA-A*01:01:24
HLA-A*01:01:25
HLA-A*01:01:26
HLA-A*01:01:27
HLA-A*01:01:28
HLA-A*01:01:29
HLA-A*01:01:30
HLA-A*01:01:31
HLA-A*01:01:32
HLA-A*01:01:33
HLA-A*01:01:34
HLA-A*01:01:35
HLA-A*01:01:36
HLA-A*01:01:37
HLA-A*01:01:38L
HLA-A*01:01:39
HLA-A*01:01:40
HLA-A*01:01:41
HLA-A*01:01:42
HLA-A*01:01:43
HLA-A*01:01:44
HLA-A*01:01:45
HLA-A*01:01:46
HLA-A*01:01:47
HLA-A*01:01:48
HLA-A*01:01:49
HLA-A*01:01:50
HLA-A*01:01:51
HLA-A*01:01:52
HLA-A*01:01:53
HLA-A*01:01:54
HLA-A*01:01:55
HLA-A*01:01:56
HLA-A*01:01:57
HLA-A*01:01:58
HLA-A*01:01:59
HLA-A*01:01:60
HLA-A*01:01:61
HLA-A*01:01:62
HLA-A*01:01:63
HLA-A*01:01:64
HLA-A*01:01:65
HLA-A*01:01:66
HLA-A*01:01:67
HLA-A*01:01:68
HLA-A*01:01:69
HLA-A*01:01:70
HLA-A*01:01:71
HLA-A*01:01:72
HLA-A*01:01:73
HLA-A*01:01:74
HLA-A*01:01:75
HLA-A*01:01:76
HLA-A*01:01:77
HLA-A*01:01:78
HLA-A*01:01:79
HLA-A*01:01:80
HLA-A*01:01:81
HLA-A*01:01:82
HLA-A*01:01:83
HLA-A*01:01:84
HLA-A*01:01:85
HLA-A*01:01:86
HLA-A*01:01:87
HLA-A*01:01:88
HLA-A*01:01:89
HLA-A*01:02
HLA-A*01:03:01:01
HLA-A*01:03:01:02
HLA-A*01:04:01:01N
HLA-A*01:04:01:02N
HLA-A*01:06
HLA-A*01:07
HLA-A*01:08
HLA-A*01:09:01:01
HLA-A*01:09:01:02
HLA-A*01:09:02
HLA-A*01:10
HLA-A*01:11N
HLA-A*01:12
HLA-A*01:13
HLA-A*01:14
HLA-A*01:15N
HLA-A*01:16N
HLA-A*01:17
HLA-A*01:18N
HLA-A*01:19
HLA-A*01:20
HLA-A*01:21
HLA-A*01:22N
HLA-A*01:23
HLA-A*01:24
HLA-A*01:25
HLA-A*01:26
HLA-A*01:27N
HLA-A*01:28
HLA-A*01:29
HLA-A*01:30
HLA-A*01:31N
HLA-A*01:32
HLA-A*01:33
HLA-A*01:35
HLA-A*01:36
HLA-A*01:37
HLA-A*01:38
HLA-A*01:39
HLA-A*01:40
HLA-A*01:41
HLA-A*01:42
HLA-A*01:43
HLA-A*01:44
HLA-A*01:45
HLA-A*01:46
HLA-A*01:47
HLA-A*01:48
HLA-A*01:49
HLA-A*01:50
HLA-A*01:51
HLA-A*01:52:01N
HLA-A*01:52:02N
HLA-A*01:53N
HLA-A*01:54
HLA-A*01:55
HLA-A*01:56N
HLA-A*01:57N
HLA-A*01:58
HLA-A*01:59
HLA-A*01:60
HLA-A*01:61
HLA-A*01:62
HLA-A*01:63
HLA-A*01:64
HLA-A*01:65
HLA-A*01:66
HLA-A*01:67:01
HLA-A*01:67:02
HLA-A*01:68
HLA-A*01:69:01
HLA-A*01:69:02
HLA-A*01:70
HLA-A*01:71
HLA-A*01:72
HLA-A*01:73
HLA-A*01:74
HLA-A*01:75
HLA-A*01:76
HLA-A*01:77
HLA-A*01:78
HLA-A*01:79
HLA-A*01:80
HLA-A*01:81
HLA-A*01:82
HLA-A*01:83:01
HLA-A*01:83:02
HLA-A*01:84
HLA-A*01:85
HLA-A*01:86
HLA-A*01:87N
HLA-A*01:88:01
HLA-A*01:88:02
HLA-A*01:88:03
HLA-A*01:89
HLA-A*01:90
HLA-A*01:91
HLA-A*01:92
HLA-A*01:93
HLA-A*01:94
HLA-A*01:95
HLA-A*01:96
HLA-A*01:97
HLA-A*01:98
HLA-A*01:99
HLA-A*01:100
HLA-A*01:101
HLA-A*01:102
HLA-A*01:103
HLA-A*01:104
HLA-A*01:105
HLA-A*01:106
HLA-A*01:107
HLA-A*01:108
HLA-A*01:109
HLA-A*01:110
HLA-A*01:111
HLA-A*01:112
HLA-A*01:113
HLA-A*01:114
HLA-A*01:115
HLA-A*01:116
HLA-A*01:117
HLA-A*01:118
HLA-A*01:119
HLA-A*01:120
HLA-A*01:121
HLA-A*01:122
HLA-A*01:123N
HLA-A*01:124
HLA-A*01:125
HLA-A*01:126
HLA-A*01:127
HLA-A*01:128
HLA-A*01:129
HLA-A*01:130
HLA-A*01:131
HLA-A*01:132
HLA-A*01:133
HLA-A*01:134
HLA-A*01:135
HLA-A*01:136
HLA-A*01:137
HLA-A*01:138
HLA-A*01:139
HLA-A*01:140
HLA-A*01:141
HLA-A*01:142
HLA-A*01:143
HLA-A*01:144
HLA-A*01:145
HLA-A*01:146
HLA-A*01:147Q
HLA-A*01:148
HLA-A*01:149
HLA-A*01:150
HLA-A*01:151
HLA-A*01:152
HLA-A*01:153
HLA-A*01:154
HLA-A*01:155
HLA-A*01:156
HLA-A*01:157
HLA-A*01:158
HLA-A*01:159
HLA-A*01:160N
HLA-A*01:161
HLA-A*01:162N
HLA-A*01:163
HLA-A*01:164
HLA-A*01:165
HLA-A*01:166
HLA-A*01:167
HLA-A*01:168
HLA-A*01:169
HLA-A*01:170
HLA-A*01:171
HLA-A*01:172
HLA-A*01:173
HLA-A*01:174
HLA-A*01:175
HLA-A*01:176
HLA-A*01:177
HLA-A*01:178N
HLA-A*01:179N
HLA-A*01:180
HLA-A*01:181
HLA-A*01:182
HLA-A*01:183
HLA-A*01:184
HLA-A*01:185
HLA-A*01:186N
HLA-A*01:187
HLA-A*01:188
HLA-A*01:189
HLA-A*01:190
HLA-A*01:191
HLA-A*01:192
HLA-A*01:193
HLA-A*01:194
HLA-A*01:195
HLA-A*01:196
HLA-A*01:197
HLA-A*01:198
HLA-A*01:199
HLA-A*01:200
HLA-A*01:201
HLA-A*01:202
HLA-A*01:203
HLA-A*01:204
HLA-A*01:205
HLA-A*01:206
HLA-A*01:207
HLA-A*01:208Q
HLA-A*01:209
HLA-A*01:210
HLA-A*01:211
HLA-A*01:212
HLA-A*01:213
HLA-A*01:214
HLA-A*01:215
HLA-A*01:216
HLA-A*01:217
HLA-A*01:218
HLA-A*01:219
HLA-A*01:220
HLA-A*01:221
HLA-A*01:222
HLA-A*01:223
HLA-A*01:224
HLA-A*01:225
HLA-A*01:226
HLA-A*01:227
HLA-A*01:228Q
HLA-A*01:229
HLA-A*01:230
HLA-A*01:231
HLA-A*01:232
HLA-A*01:233
HLA-A*01:234
HLA-A*01:235
HLA-A*01:236
HLA-A*01:237
HLA-A*01:238
HLA-A*01:239
HLA-A*01:240N
HLA-A*01:241
HLA-A*01:242
HLA-A*01:243
HLA-A*01:244
HLA-A*01:245
HLA-A*01:246
HLA-A*01:247N
HLA-A*01:248Q
HLA-A*01:249
HLA-A*01:250N
HLA-A*01:251
HLA-A*01:252
HLA-A*01:253
HLA-A*01:254
HLA-A*01:255
HLA-A*01:256
HLA-A*01:257
HLA-A*01:258N
HLA-A*01:259
HLA-A*01:260
HLA-A*01:261