secretory component

https://doi.org/10.1351/goldbook.13665
Proteolytic cleavage product of the poly-Ig receptor which remains associated with dimeric immunoglobulin A (IgA) in sero-mucus secretions.
Source:
PAC, 2012, 84, 1113. (IUPAC glossary of terms used in immunotoxicology (IUPAC Recommendations 2012)) on page 1242 [Terms] [Paper]