Reagent/Resource	Reference or source	Identifier or catalog number
Experimental models
Mouse: B6.SJL‐Ptprcapepcb/BoyJ	The Jackson Laboratory	JAX: 002014
Mouse: C57BL/6	The Jackson Laboratory	JAX: 000664
Mouse: PGT121 κ KI mouse model	This paper	N/A
Mouse: CLK21 BCR KI mouse model	This paper	N/A
Mouse: CLK09 BCR KI mouse model	This paper	N/A
Antibodies
PerCP/Cy5.5 anti‐mouse CD45.1 Antibody	BioLegend	Cat#: 110728
PE‐Cy™7 Hamster Anti‐Mouse CD95	BD Biosciences	Cat#: 557653
Brilliant Violet 785™ anti‐mouse CD45.2	BioLegend	Cat#: 109839
anti‐mouse CD38, BV510	BD Biosciences	Cat#: 740129
Pacific Blue™ anti‐mouse/human CD45R/B220 Antibody	BioLegend	Cat#: 103227
BV711 Rat Anti‐Mouse Ig, λ1, λ2 & λ3 Light Chain	BD Biosciences	Cat#: 744527
BUV395 Rat Anti‐Mouse Ig, κ light chain	BD Biosciences	Cat#: 742839
APC/Cy7 anti‐mouse/human CD45R/B220 Antibody	BioLegend	Cat#: 103224
BV421 Rat Anti‐Mouse IgM	BD Biosciences	Cat#: 743323
PE/Cy7 anti‐mouse IgD Antibody	BioLegend	Cat#: 405720
PE anti‐mouse CD45.2 Antibody	BioLegend	Cat#: 109808
Anti‐mouse CD38 Alexa700	Invitrogen	Cat#: 56‐0381‐82
BV786 Rat Anti‐Mouse IgD	BD Biosciences	Cat#: 563618
BV510 Rat Anti‐Mouse B220/CD45R Clone RA3‐6B2	BD Biosciences	Cat#: 563103
BV421 Rat Anti‐Mouse IgG1	BD Biosciences	Cat#: 562580
BUV395 Rat Anti‐Mouse IgM	BD Biosciences	Cat#: 743329
PE anti‐mouse CD80 antibody	BioLegend	Cat#: 104708
APC/Cyanine7 anti‐mouse CD73 Antibody	BioLegend	Cat#: 127232
GL7 Monoclonal Antibody (GL‐7 (GL7)), eFluor 450	Thermo Fisher	Cat#: 48‐5902‐82
BUV395 Rat Anti‐Mouse CD273	BD Biosciences	Cat#: 565102
CD4 Monoclonal Antibody (GK1.5), APC‐eFluor 780	Invitrogen	Cat#: 47‐0042‐80
CD8a Monoclonal Antibody (53‐6.7), APC‐eFluor 780	Invitrogen	Cat#: 47‐0081‐80
F4/80 Monoclonal Antibody (BM8), APC‐eFluor 780	Invitrogen	Cat#: 47‐4801‐80
Ly‐6G Monoclonal Antibody (1A8‐Ly6g), APC‐eFluor 780	Invitrogen	Cat#: 47‐5931‐80
Alexa Fluor® 488 anti‐mouse CD38 Antibody	BioLegend	Cat#: 102714
Alexa Fluor® 647 anti‐mouse/human GL7 Antigen	BioLegend	Cat#: 144606
Alexa Fluor® 594 anti‐mouse/human CD45R/B220 Antibody	BioLegend	Cat#: 103254
Alkaline Phosphatase AffiniPure Goat Anti‐Mouse IgG, Fcγ Fragment Specific	Jackson ImmunoResearch	Cat#: 115‐055‐071
Purified Rat Anti‐Mouse CD16/CD32 (Mouse BD Fc Block™	BD Biosciences	Cat#: 553142
Alexa Fluor® 488 anti‐mouse CD45.2 Antibody	BioLegend	Cat#: 109816
Alexa Fluor® 594 anti‐mouse CD3 Antibody	BioLegend	Cat#: 100240
Oligonucleotides and other sequence‐based reagents
TaqMan probes for genotyping	TransnetYX	Appendix Table S1
Primers for RT–PCR	GENEWIZ	Appendix Table S6
Index primers for NGS,	Integrated DNA Technologies	Appendix Table S7
sgRNA	Synthego	Table 1
Chemicals, enzymes and other reagents
LIVE/DEAD™ Fixable Blue Dead Cell Stain Kit, for UV excitation	Thermo Fisher Scientific	Cat#: L34962
Alexa Fluor 488 Streptavidin	BioLegend	Cat#: 405235
Alexa Fluor 647 Streptavidin	BioLegend	Cat#: 405237
Alexa Fluor 594 Streptavidin	BioLegend	Cat#: 405240
Pan B‐Cell Isolation Kit II, mouse	Miltenyi Biotec	Cat#: 130‐104‐443
SuperScript™ III Reverse Transcriptase	Thermo Fisher	Cat#: 18080085
RNeasy® Protect Animal Blood Kit	Qiagen	Cat#:73224
Maxima First Strand cDNA Synthesis Kit	Thermo Fisher Scientific	Cat#: K1672
PrimeSTAR® HS DNA Polymerase premix	Takarabio	Cat#: R040A
HIFI HOTSTART READYMIX 500RXN	Kapa Biosystems	Cat#: KK2602
HotStarTaq DNA Polymerase	Qiagen	Cat#: 203205
RNasin® Ribonuclease Inhibitors (Recombinant)	Promega	Cat#: N2515
CountBright™ Absolute Counting Beads, for flow cytometry	Thermo Fisher Scientific	Cat#: C36950
SIGMAFAST™ p‐Nitrophenyl phosphate Tablets	Sigma	Cat#: N2770‐50SET
NP40	Millipore	Cat#: 492016‐100ML
UltraComp eBeads™ Compensation Beads	Thermo Fisher Scientific	01‐2222‐42
Tissue‐Tek® O.C.T. Compound, Sakura® Finetek	VWR	25608‐930
eOD‐GT8 60mer	Jardine et al (2015)	N/A
eOD‐GT8 KO 60mer	Jardine et al (2015)	N/A
eOD‐GT8 soluble protein	Sok et al (2016)	N/A
eOD‐GT8 KO soluble protein	Sok et al (2016)	N/A
Software
Flowjo X	Treestar	https://www.flowjo.com/
Prism 8	GraphPad	https://www.graphpad.com/
Microsoft Office	Microsoft	https://www.office.com/
IMGT/V‐quest		http://www.imgt.org/IMGTindex/V‐QUEST.php
Geneious Prime	Biomatters	https://www.geneious.com/
Other
Master Cycler PCR machine	Eppendorf
ELISA readers	BioTek
Zeiss Elyra PS.1 confocal microscope	Zeiss
5 laser LSR Fortessa	BD