CD200 -dependent and -independent immune-modulatory functions of neural stem cells

Neural stem/precursor cells (NPC) exhibit powerful immune-modulatory properties. Attenuation of neuroinflammation by intra-cerebroventricular transplantation of NPC, protects from immune-mediated demyelination and axonal injury. The immune modulatory properties of NPC are mediated by a non-species-specific, multiple bystander effect, mediated by both direct cell-cell contact, and by soluble factor(s). CD200 is a cell-surface molecule, with important roles in regulating diverse immune responses, and shown also to limit neuroinflammatory processes. We hypothesized that CD200 may play a role in mediating immune-modulatory effects of NPC. We used wild type and CD200-deficient NPC to examine the role of CD200 in mediating two vital aspects of NPC -immune modulatory properties: (1) Attenuation of autoimmune neuroinflammation; and (2) Suppression of immune rejection response towards transplanted allogeneic NPC from the host CNS. We found that CD200 is dispensable for attenuating acute experimental autoimmune neuroinflammation, but is required for protecting transplanted allogeneic NPC from immune rejection by the host tissue. CD200 deficient NPC showed similar growth, differentiation and survival properties as wild type NPC. CD200-deficient NPC attenuated efficiently T cell activation and proliferation, but exhibited reduced ability to inhibit macrophages. We conclude that CD200 plays a partial role in mediating the immune-modulatory properties of NPC. The differential effect on T cells versus macrophages may underlie the observed discrepancy in their function in vivo.