Table 1.

Experimental evidence for tissue-resident lymphocyte subsets in the kidney

Cell Subset	Model System and Methods	Main Finding Regarding Lymphocyte Tissue Residency in the Kidney	Ref.
NK cells	Mouse, IRI	CD49a+DX5− NK cells are kidney resident	32
	Parabiosis, antibody-mediated depletion of circulating NK cells	Kidney-resident NK cells promote IRI
NK cells	Renal biopsies of patients showing different degrees of kidney fibrosis	CD69+ NK cells produce IFN-γ and accumulate in fibrotic kidney tissue	34
	CD69 expression by flow cytometry
CD8+ T cells	Mouse, VSV, and listeria infection	Pathogen-specific CD8+ T cells show long-term persistence in the kidney tissue	8
	Ag-loaded tetramer staining
CD8+ T cells	Mouse, LCMV infection	Tissue residence of renal LCMV-specific CD8+ T cells	72
	Parabiosis, intravascular leukocyte labeling	S1P1 expression prevents renal Trm cell accumulation
		Continuous TCR signaling is not required for Trm cell persistence
CD8+ and CD4+ T cells	Mouse, LCMV infection, tumor	i.v. mAb-negative CD69+ CD103± CD4+ and CD8+ Trm cells are found in the kidney tissue	20
	Intravascular leukocyte labeling
CD8+ T cells	Mouse, LCMV, and VSV infection	Standard protocols for T cell isolation are inefficient	17
	Quantitative immunofluorescence microscopy, intravascular leukocyte labeling	Resident T cells greatly outnumber recirculating cells in nonlymphoid tissues
CD8+ T cells	Mouse, LCMV infection	The transcription factors Blimp1 and Hobit are required for renal Trm development	78
	Ag-loaded tetramer staining
CD8+ T cells	Mouse, LCMV infection	TGF-β is required for transendothelial migration of Trm cells into the kidney	71
	Intravascular leukocyte labeling

VSV, varicella zoster virus; Ag, antigen; LCMV, lymphocytic choriomeningitis virus; S1P1, sphingosine phosphate 1 receptor 1, TCR, T cell receptor.