Immune regulation of neuronal injury and repair by observing T cell activation

Abstract

Background and Hypothesis: 

It is unknown how the immune system maintains the majority of facial motoneuron (FMN) survival after axotomy. IL-10 cytokine is necessary for FMN survival and CD4+ T cells are activated and play a critical role in survival, but do not produce IL-10. It was proposed that the source of IL-10 resides in the CNS; however, it is possible that antigen presenting cells (APC) produce IL-10 which activate CD4+ T cells to a neuroprotective phenotype. The regulation of IL-10 receptors (IL-10R) in immunodeficient compared to wild-type (WT) mice in the facial nucleus was studied in this experiment, as well as the possibility of the PNS producing IL-10. 

Experimental Design or Project Methods: 

To study APC’s role in motoneuron survival, we transferred WT whole splenocytes into global IL-10 knock out (KO) mice prior to axotomy. To study IL-10R gene expression, immunodeficient RAG-2 KO mice received WT or IL-10R-/- CD4+ T cells prior to axotomy.  

Results: 

qPCR revealed that WT mice upregulate IL-10R after axotomy, whereas RAG-2 KO mice had decreased expression comparatively. RAG-2 mice who received WT CD4+ T cells transfer restored IL-10R comparable to WT values.IL-10R was rescued in RAG-2 mice after the adoptive transfer of WT CD4+T cells. When IL-10R-/- CD4+ cells were transferred into RAG-2 mice, IL-10R values were restored; however, these T cells were unable to rescue FMN survival.  

Conclusion and Potential Impact: 

If WT whole splenocytes transferred into global IL-10 KO mice rescue FMN survival, it implies that APC play a role in producing IL-10. If they cannot mediate rescue, then peripheral IL-10 is unlikely sufficient for FMN survival. CD4+ T cells regulate central IL-10R response and must respond to IL-10 to mediate FMN survival. The transfer of whole splenocytes provides APCs capable of producing IL-10 and CD4+ T cells capable of responding to IL-10.