naïve lymphocyte

https://doi.org/10.1351/goldbook.13496
Mature T cell or B cell that has not yet been activated (see lymphocyte activation) by encounter with antigen.
Source:
PAC, 2012, 84, 1113. (IUPAC glossary of terms used in immunotoxicology (IUPAC Recommendations 2012)) on page 1218 [Terms] [Paper]