IMGT Antibody Numbering

abYsis supports all major numbering systems. The IMGT numbering scheme is a popular scheme for numbering residues in an antibody in a consistent manner. However the scheme is now known to have limitations:

IMGT Details

The IMGT numbering scheme differs from others by avoiding insertion codes (such as 27A, 27B etc) and instead defining the longest antibody sequence possible and instead removing residues.

In principle this is attractive but in practice has disadvantages.

Firstly, despite efforts to defined the longest antibody sequence, some organisms have unusually long CDRs and furthermore humans are very inventive, generating antibodies with characteristics that are not normally seen.

Secondly the insertion letters in practice are a very convenient way to alert the eye to positions of particular interest rather than having to scan a sequences for missed numbers.

Early implementations of this scheme placed all insertions at the ends of CDRs which is not structurally correct though recent changes have rectified this. (Brochet et al. 2008)