Reagent or Resource	Source	Identifier
Antibodies
Mouse anti‐human CD86 (Alexa Fluor 647)	BioLegend	Cat#: 305416
Human TruStain FcX (FcR blocking)	BioLegend	Cat#: 422302
Phospho‐Erk1/2 (Thr202/Tyr204) mAb (Alexa Fluor 488)	CST	Cat#: 4374S
Rabbit anti‐phospho‐FOS (Ser32) mAb	CST	Cat#: 5348S
Rabbit anti‐human FOS mAb	CST	Cat#: 2250S
Mouse anti‐human CD69 (Alexa Fluor 647)	BioLegend	Cat#: 310918
Mouse anti‐human CD3 (Alexa Fluor 647)	BioLegend	Cat#: 300322
Mouse anti‐human CD20 (Brilliant Violet 605)	BioLegend	Cat#: 302334
Mouse anti‐human CD137 (Brilliant Violet 421)	BioLegend	Cat#: 309820
Bacterial and virus strains
Escherichia coli DH5alpha	Thermo Fisher	Cat#: 18265017
Chemicals, peptides, and recombinant proteins
A/C dimerizer (AP21967)	Takara	Cat#: 635057
Indo‐1 LR (AM)	TEFLabs	Cat#: TEF0145
Pluronic F‐127	Sigma‐Aldrich	Cat#: P2443
Lenti‐X concentrator	Takara	Cat#: 631231
Perm buffer III	BD	Cat#: 558050
Critical commercial assays
RNeasy Plus Mini Kit	Qiagen	Cat#: 74134
QIAshredder	Qiagen	Cat#: 79654
SuperScript IV VILO Master Mix with ezDNase	Thermo Fisher	Cat#: 11756050
TaqMan Advanced Fast Master Mix	Thermo Fisher	Cat#: 13428456
GAPDH TaqMan assay	Thermo Fisher	Hs02786624_g1
PGK1 TaqMan assay	Thermo Fisher	Hs00943178_g1
CD69 TaqMan assay	Thermo Fisher	Hs01119267_g1
FOS TaqMan assay	Thermo Fisher	Hs00934033_m1
IL2 TaqMan assay	Thermo Fisher	Hs00174114_m1
CXCL8 (IL8) TaqMan assay	Thermo Fisher	Hs00174103_m1
TNFRSF9 (CD137) TaqMan assay	Thermo Fisher	Hs00155512_m1
Experimental models: cell lines
HEK‐293T: human adherent cell line	ATCC	Cat#: CRL‐11268
J.NFAT: derived from human Jurkat T‐cell leukemia line	(James, 2018)	N/A
Raji‐FRBEx: derived from human B‐cell lymphoma line	(James & Vale, 2012)	N/A
Oligonucleotides
For primer sequences, see Appendix Fig S3	This work	N/A
Recombinant DNA
pCMVΔR8.91	(Zufferey et al, 1997)	N/A
pMD2.G	Gift from Didier Trono	Addgene#: 12259
pHR‐OptoCAR‐mScarlet	This work	Addgene#: 170463
pHR‐iRFP670‐CaaX	This work	Addgene#: 170464
pHEFI‐OptoCARCD19‐mScarlet	This work	Addgene#: 170465
Software and algorithms
Fiji (ImageJ): image analysis	(Schindelin, Arganda‐Carreras et al, 2012)	https://fiji.sc/
MATLAB R2019a: data processing	MathWorks	N/A
FlowJo V10.2: data processing	FlowJo LLC	N/A
Excel 365	Microsoft	N/A
Illustrator 2020	Adobe	N/A