T cell repertoire analyses in neonatally tolerized mice

Previously, it was shown that SJL/J mice given Ig-PLPI in saline at the neonatal stage were resistant to the induction of Experimental Allergic Encephalomyelitis (EAE) later in life (21). Contributing to this resistance were T cells which displayed a unique phenotype consisting of IFN-y mediated anergy in the spleen, and Th2 deviation in the lymph nodes (21). The objective of these studies was to investigate whether differences in the T cell repertoires between the lymph node and spleen contributed to this organ specific modulation of disease. This was achieved by immortalizing PLP 1 specific T cell hybridomas from both lymphoid organs and analyzing their T cell receptors. Specifically, the T cell receptor beta chains were analyzed for their variable (V), diversity (D), and joining (J) gene segment usage to see whether or not a particular gene segment may be involved in the responses. Additionally, the CDR3 regions were analyzed by their lengths and amino acid composition to gain further insight about the antigen binding site. It was found that there was no restriction in the V, D, or J gene usage, in either the spleen or lymph node T cells. However, in analyzing the CDR3 region of the TCRs, a Glycine-Glycine motif was found in the cells from the lymph node. The splenic T cells did not contain this motif in their CDR3 regions. Therefore, it can be postulated that this G1y-G1y motif creates a structural change in the TCRs from the lymph node and this difference may contribute to a different binding affinity of the TCR toward the peptide and thus lead to the organ specific responses previously seen.