title: Unexpected lack of specificity of a rabbit polyclonal TAP-L (ABCB9) antibody.
abstract: In this article, we describe the surprising non-specific reactivity in immunoblots of a rabbit polyclonal antibody (ref. Abcam 86222) expected to recognize the transporter associated with antigen processing like (TAP-L, ABCB9) protein. Although this antibody, according to company documentation, recognizes a band with the expected molecular weight of 84 kDa in HeLa, 293T and mouse NIH3T3 whole-cell lysates, we found that this band is also present in immunoblots of TAP-L deficient bone marrow-derived dendritic cell (BMDC) whole-cell lysates in three independent replicates. We performed extensive verification by multiple PCR tests to confirm the complete absence of the ABCB9 gene in our TAP-L deficient mice. We conclude that the antibody tested cross-reacts with an unidentified protein present in TAP-L knockout cells, which coincidentally runs at the same molecular weight as TAP-L. These findings underline the pitfalls of antibody specificity testing in the absence of cells lacking expression of the target protein.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM) U1151, Paris, 75015, France; Centre national de la recherche scientifique (CNRS), Unité mixte de recherche (UMR) 8253, Paris, 75015, France; Université Paris Descartes, Sorbonne Paris Cité, 75015, France.
authors.forename: Peter
authors.initials: P
authors.lastname: van Endert
authors.affiliation: Institut National de la Santé et de la Recherche Médicale (INSERM) U1151, Paris, 75015, France; Centre national de la recherche scientifique (CNRS), Unité mixte de recherche (UMR) 8253, Paris, 75015, France; Université Paris Descartes, Sorbonne Paris Cité, 75015, France.
authors.forename: Myriam
authors.initials: M
authors.lastname: Lawand
keywords: ABCB9; MHC; TAP-L transporter; antigen presentation; dendritic cell; lysosome; peptide