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IMGT reference sequences in FASTA format:

Amino acid sequences without 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) 
>AF327184|ICOS*01|Mus musculus|F|EX1|
MKPYFCRVFVFCFLIRLLT
>AF327185|ICOS*01|Mus musculus|F|EX2|[D]|V-LIKE|
GEINGSADHRMFSFHNGGVQISCKYPETVQQLKMRLFREREVLCELTKTKGSGNAVSIKN
PMLCLYHLSNNSVSFFLNNPDSSQGSYYFCSLSIFDPPPFQERNLSGGYLHIY
>AF327185|ICOS*01|Mus musculus|F|EX3|
ESQLCCQLKLWLPVGCAAFVVVLLFGCILIIWFSKK
>AF327185|ICOS*01|Mus musculus|F|EX4|
KYGSSVHDPNSEYMFMAAVNTNKKSRLA
>AF327185|ICOS*01|Mus musculus|F|EX5|
GVTS
>ICOS*01|Mus musculus|F|EX1-EX5|Splicing A|complete|
MKPYFCRVFVFCFLIRLLTGEINGSADHRMFSFHNGGVQISCKYPETVQQLKMRLFRERE
VLCELTKTKGSGNAVSIKNPMLCLYHLSNNSVSFFLNNPDSSQGSYYFCSLSIFDPPPFQ
ERNLSGGYLHIYESQLCCQLKLWLPVGCAAFVVVLLFGCILIIWFSKKKYGSSVHDPNSE
YMFMAAVNTNKKSRLAGVTS*