Antisecretory Factor (AF)/S5a, was identified through its ability to counteract pathological secretion. AF is also a neuromodulater and have anti-inflammatory actions. Furthermore, AF/S5a, is an important component of the proteasome. AF has a calculated molecular mass of 41 kDa and a pI of 4.7. No family of AF-like proteins has been identified. AF has multiple functions in the cell and it is possible that different forms exist as a result of post-translational modifications. In the present study eight epitope-specific antibodies covering the entire length of AF was used to investigate if modified forms of AF could be detected in the porcine spinal cord. Immunoblots, 2D gels and immunohistochemistry (IHC) were used. Immunoblots and 2D gels showed that all antisera detected a single protein with similar molecular mass and pI. However, IHC on tissue sections revealed an epitope-specific sub-cellular staining pattern. Antisera recognizing epitopes in the N-terminal part of AF, containing the antisecretory activity, showed a more restricted localization than antisera directed at the C-terminal part, containing the ubiquitin binding sites. We suggest that AF/S5a can exist in several conformation variants. Such conformational changes could be of functional importance.