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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) 
>M37812|CD28*01|Homo sapiens|F|EX1|
MEHSTFLSGLVLATLLSQ
>M37813|CD28*01|Homo sapiens|F|EX2|[D]|V-LIKE|
GNKILVKQSPMLVAYDNAVNLSCKYSYNLFSREFRASLHKGLDSAVEVCVVYGNYSQQLQ
VYSKTGFNCDGKLGNESVTFYLQNLYVNQTDIYFCKIEVMYPPPYLDNEKSNGTIIHVK
>M37814|CD28*01|Homo sapiens|F|EX3|
GKHLCPSPLFPGPSKPFWVLVVVGGVLACYSLLVTVAFIIFW
>M37815|CD28*01|Homo sapiens|F|EX4|
VRSKRSRLLHSDYMNMTPRRPGPTRKHYQPYAPPRDFAAYRS
>CD28*01|Homo sapiens|F|EX1-EX4|Splicing A|complete|
MLRLLLALNLFPSIQVTGNKILVKQSPMLVAYDNAVNLSCKYSYNLFSREFRASLHKGLD
SAVEVCVVYGNYSQQLQVYSKTGFNCDGKLGNESVTFYLQNLYVNQTDIYFCKIEVMYPP
PYLDNEKSNGTIIHVKGKHLCPSPLFPGPSKPFWVLVVVGGVLACYSLLVTVAFIIFWVR
SKRSRLLHSDYMNMTPRRPGPTRKHYQPYAPPRDFAAYRS