accessory molecule

https://doi.org/10.1351/goldbook.12831
Molecule other than immunoglobulin (Ig), T-cell receptor (TCR), or major histocompatibility complex (MHC) molecule that participates in T lymphocyte recognition and response to antigen.
Source:
PAC, 2012, 84, 1113. (IUPAC glossary of terms used in immunotoxicology (IUPAC Recommendations 2012)) on page 1116 [Terms] [Paper]