N-terminal PAX8 polyclonal antibody shows cross-reactivity with N-terminal region of PAX5 and is responsible for reports of PAX8 positivity in malignant lymphomas

Lucas Moretti, L. Jeffrey Medeiros, Kranthi Kunkalla, Michelle D. Williams, Rajesh R. Singh, Francisco Vega

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30 Scopus citations


Recently, reports using immunohistochemistry and a polyclonal antibody directed against the N-terminal region of PAX8 describe PAX8 expression in malignant lymphomas. As the N-terminal regions of PAX family members, including the B-cell transcription factor PAX5, have high sequence homology, we investigated PAX8 positivity in malignant lymphomas. Comparative sequence analysis between the N-and C-terminal regions of PAX8 and PAX5 proteins confirmed homologies of 70% and 39%, respectively. We then compared the results using N-terminal (high homology) and C-terminal (lower homology) anti-PAX8 antibodies to assess PAX8 expression in reactive tissues, diffuse large B-cell lymphoma and classical Hodgkin lymphoma, using routine immunohistochemical methods. Expression of PAX8 was also assessed in diffuse large B-cell lymphoma and classical Hodgkin lymphoma cell lines using real-time qRT-PCR methods. Our results show that reactive and neoplastic B-cells are positive for PAX8 using the N-terminal antibody, but negative for PAX8 when the C-terminal antibody was used. PAX8 mRNA levels were not detected in any of the B-cell lymphoma cell lines studied. These results indicate that benign and malignant B-cells do not express PAX8. We conclude that positivity for PAX8 reported by others in B-cell lymphomas is likely due to cross-reactivity between the N-terminal regions of PAX8 and PAX5, due to the high sequence homology of these two regions.

Original languageEnglish
Pages (from-to)231-236
Number of pages6
JournalModern Pathology
Issue number2
StatePublished - Feb 1 2012
Externally publishedYes



  • B-cell lymphomas
  • cross-reactivity
  • immunohistochemistry
  • PAX5
  • PAX8

ASJC Scopus subject areas

  • Pathology and Forensic Medicine

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