TABLE 1.

Molecules that are expressed both in the nervous system and immune system, and their reported/potential functions.

Neuro-immune common molecule		Nervous system			Immune system
		Expression	Function	References (bold: review)	Expression	Function	References (bold: review)
Major histocompatibility complex (MHC) class I	H2-Kb, H2-Db	Neuron, glial cells	Regulate axonal and dendritic growth, synaptic density, synaptic transmission, activity-dependent refinement and plasticity	Elmer and McAllister, 2012; McAllister, 2014	All nucleated cells, platelet	Present antigen to T cells, activate NK cells if missing or changed	Blum et al., 2013; Vivier et al., 2011
Complement family	C1q, C2-9	Neuron, glial cells	Regulate activity-dependent synaptic pruning, related to neurogenesis, migration, and neuronal survival	Veerhuis et al., 2011;Stephan et al., 2012	Epithelial cell, monocyte/macrophage, fibroblast, hepatocyte	Eliminate cellular debris and infectious microbes, orchestrate immune responses	Ricklin et al., 2010
	CR3	Microglia			neutrophil, macrophage, NK cell
Fc receptor	FcγR II B	Purkinje cell	Regulate the development of Purkinje cell	Nakamura et al., 2007	B cell, monocyte/macrophage, neutrophil, dendritic cell, basophil	Low affinity receptor for the Fc region of IgG and negatively regulate receptor-induced signaling	Bruhns, 2012
	Fcα/μR	Oligodendrocyte precursor cell (OPC)	Regulate proliferation and maturation of OPC	Tanabe and Yamashita, 2018a	B cell, macrophage	Work as a receptor for the Fc region of IgA and IgM	Shibuya et al., 2000
CD3 family	CD3ϵ	Purkinje cell	Regulate the development of Purkinje cell	Nakamura et al., 2007	T cell	Work as a co-receptor for TCR	Kuhns et al., 2006
	CD3ζ	dLGN, hippocampal neuron	Regulate activity-dependent synapse formation of RGCs in retina, LTP and LTD, and promote axon pruning	Huh et al., 2000; Baudouin et al., 2008; Xu et al., 2010, Elmer and McAllister, 2012
Cytokine	IL-1β, IL-6, TNF-α, TGF-β	Neuron, microglia, astrocyte	Regulate cell survival, proliferation and differentiation, axonal growth and synaptogenesis	Bauer et al., 2007; Knuesel et al., 2014	Several immune cells, fibroblast, endotherial cell	Play key roles in mediating inflammatory and anti-inflammatory reactions	Arango Duque and Descoteaux, 2014
Chemokine	CXCL1 (fractalkine)	Neuron	Regulate microglial recruitment, neuronal survival, synaptic maturation, activity and plasticity, synaptic pruning	Paolicelli et al., 2014	Monocyte/macrophage, fibroblast, epithelial cell, endothelial cell	Survival, migration and adhesion of monocyte	Imai et al., 1997
	CX3CR1	Microglia			Monocyte/macrophage, T cell subset, platelet, NK cell
	CXCL12 (SDF-1)	Cerebral cortex (subplate,ventricular surface)	Enhance migration of microglia, NPC, cortical interneuron and Cajal Retzius cell, related to axon guidance, neurite outgrowth	Li and Ransohoff, 2008; Zhu and Murakami, 2012; Guyon, 2014	Bone marrow	Essential for development of B cell and homing of hematopoietic stem cell to the bone marrow	Nagasawa, 2015
	CXCR4	Neuron			Several immune cells including hematopoietic stem cell
TLR	TLR2, 3, 4, 8, 9	Neuron, neuronal progenitor cell (NPC), microglia, astrocyte, oligodendrocyte	Related to axon outgrowth, NPC proliferation, cognition, sensory and motor behaviors	Kioussis and Pachnis, 2009; Okun et al., 2011; Khariv et al., 2013	Monocyte/macrophage, dendritic cell, B cell, NK cell, regulatory T cell, neutrophil, basophil, fibroblast, epithelial cell, endothelial cell	Key molecules for innate immune system, work as a receptor for peptidoglycan (TLR2), dsRNA (TLR3), LPS (TLR4), ssRNA (TLR8), CpG DNA (TLR9)	Kawai and Akira, 2007
Pentraxin	PTX3	Astrocyte	Modulate phagocytic functions of microglia, induce functional synapse formation	Jeon et al., 2010; Fossati et al., 2019	Dendritic cell, macrophage, neutrophil	Activate complement, facilitate pathogen recognition by phagocytes	Garlanda et al., 2005
Pcdh	Pcdh18	Ventricular zone in the forbrain and midbrain	Involved in neural circuit formation	Kim et al., 2011	Activated CD8+ memory T cell	Function as an inhibitory signaling receptor and restrict the effector phase	Vazquez-Cintron et al., 2012
Dscam	Dscam	Neuron	Specify neuronal wiring, regulate axon guidance and retinal lamination	Boulanger, 2009; Schmucker and Chen, 2009	Hemolymph (in flies)	Bind directly to bacteria	Watson et al., 2005
Eph/Ephrin	Ephrin-B1	Neuron	Axon guidance during development, synaptic plasticity	Klein, 2009	Germinal center B cell, memory precursor B cell	Inhibit GC recruitment and retention of Tfh cells, promote IL-21 production	Laidlaw et al., 2017; Lu et al., 2017
Semaphorin	Sema3A	Olfactory neuron, cerebral cortex, corpus callosum	Inhibit axon branching in the cortical neurons, regulate pre-target axon sorting of olfactory system	Tran et al., 2007; Imai et al., 2009	Dendritic cell, T cell	Inhibit monocyte migration, inihibit T cell activation	Kumanogoh and Kikutani, 2013; Nishide and Kumanogoh, 2018