IMSEQ
For the IMSEQ format, the header contains the following elements, separated by "|":
- The chain: TRA, TRB, TRG or TRD for T cells, and IGH, IGK and IGL for B cells.
- The segment type: V, D, J, C.
- The segment ID. For B cells constant genes, the segment ID should also contain the letter corresponding to the encoded isotype.
- The segment allele.
- For J and V segments, the position of the first base of the conserved amino acid, counting from 0.
Currently only the heavy (IGH) and light 
and 
(IGK and IGL) chain types are supported for B cells.
Any segments with an unsupported chain or segment type are silently ignored.