TABLE 1.

Summary of experimental animal (mice) studies showing the effect of programmed cell death-1 ligands on retinal ganglion cell number

Experiment	Strain	Age	Age Rationale	Result
Retinal PD-L1 expression by IF	WT	P2	Age-match RGC quantification	Expressed in GCL cell bodies and neuroblast layer neuropil
	WT	P56	Age-match brain expression	Expressed in RGCs, bipolar cells, and Müller glia
Brain PD-1 and PD-L1 expression by IF	WT	P56	Age-matched to reference mouse brain atlas (ref)	PD-1 and PD-L1 expressed in SCs
RGC quantification by IF	WT	P2	Peak RGC death	Increased RGC number in PD-1−/− and PD-L1/L2−/−
	PD-1−/−
	PD-L1/L2"/-
	WT	P56	Age-match brain expression	Increased RGC number in PD-L1/L2−/−
	PD-1−/−
	PD-L1/L2−/−
	PD-L1−/−
	PD-L2−/−
Axon counting by electron microscopy	WT	P28	Establish baseline for future experiments	Increased RGC number in PD-L1/L2−/−
	PD-1−/−
	PD-L1/L2−/−
ERG and SD-OCT	WT	P42	Knockout animal availability	Normal outer retina function and architecture in PD-1−/− and PD-L1/L2−/−
	PD-1−/−
	PD-L1/L2−/−