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IMGT reference sequences in FASTA format:

Amino acid sequences with gaps

The FASTA header contains:
IMGT accession number | gene and allele name | species | functionality | exon name | domain name | domain type | alternative splicing (if it is) | partial (if it is) 
>AF411058|ICOS*01|Homo sapiens|F|EX1|
MKSGLWYFFLFCLRIKVLT
>AF411058|ICOS*01|Homo sapiens|F|EX2|[D]|V-LIKE|
GEINGSANYEMFIFHNGGVQILCKYPDIV.......QQFKMQLLK..GGQILCDLTKTK.
GSGNTVSIKSL....KFCHSQLSNNSVSFFLYNLDHSHANYYFCNLSIFDPPPF.KVTLT
GGYLHIY
>AF411058|ICOS*01|Homo sapiens|F|EX3|
ESQLCCQLKFWLPIGCAAFVVVCILGCILICWLTKK
>AF411058|ICOS*01|Homo sapiens|F|EX4|
KYSSSVHDPNGEYMFMRAVNTAKKSRLT
>AF411058|ICOS*01|Homo sapiens|F|EX5|
DVTL
>BC028006|ICOS*01|Homo sapiens|F|EX1|Splicing B|
MKSGLWYFFLFCLRIKVLT
>BC028006|ICOS*01|Homo sapiens|F|EX2|[D]|V-LIKE|Splicing B|
GEINGSANYEMFIFHNGGVQILCKYPDIV.......QQFKMQLLK..GGQILCDLTKTK.
GSGNTVSIKSL....KFCHSQLSNNSVSFFLYNLDHSHANYYFCNLSIFDPPPF.KVTLT
GGYLHIY
>BC028006|ICOS*01|Homo sapiens|F|EX3|Splicing B|
ESQLCCQLKFWLPIGCAAFVVVCILGCILICWLTKKM