IGKV1D-22 and rheumatoid arthritis: Due to the association between osteopontin and RA, several anti-osteopontin antibodies have been developed and studies of these antibodies in animal RA models show promising results.23–25 The antibody M5 recognizes and binds to a cryptic epitope of thrombin-cleaved mouse osteopontin (147SLAYGLR153) and thereby blocks the binding of cleaved osteopontin to α9 and α4 integrins, which result in abrogation of monocyte migration.18