bystander effect

in immunology
https://doi.org/10.1351/goldbook.12968
Positive or negative effect on the immune system seen after exposure to certain drugs, radiation, and other agents, induced by non-immune mechanisms.
Source:
PAC, 2012, 84, 1113. (IUPAC glossary of terms used in immunotoxicology (IUPAC Recommendations 2012)) on page 1137 [Terms] [Paper]