Background/Purpose:  We found that systemic lupus erythematosus (SLE) was induced experimentally by repeatedly immunizing the mice normally not prone to autoimmune diseases by any exogenous antigen so far examined (Tsumiyama K. et al. PLoS ONE 4(12):e8382, 2009). We have then proposed a novel ‘self-organized criticality theory’ that takes place when host’s immune system is overstimulated by repeated exposure to antigen to levels that surpass the immune system’s stability limit, i.e., self-organized criticality. The autoreactive lymphocyte clones, which we name autoantibody-inducing CD4 T cells (aiCD4 T cells) are newly generated via de novo T cell receptor (TCR) revision from thymus-passed non-autoreactive clones at peripheral lymphoid organs. They not only stimulated B cells to generate varieties of autoantibodies but also helped final differentiation of CD8 T cell into cytotoxic T lymphocyte (CTL) via antigen cross-presentation to induce tissue injuries identical to SLE. We here tried to identify the phenotype of aiCD4 T cell, and show that aiCD4 T cell belongs to CCR4⁺CD45RB^lo122^lo CD4 subpopulation.

Methods: BALB/c were repeatedly immunized with ovalbumin (OVA), keyhole limpet hemocyanin (KLH) or staphylococcal enterotoxin B (SEB). RF, anti-Sm and anti-dsDNA antibodies were measured using ELISA. To assign CD number on the aiCD4 T cell, expression of effector / memory markers were studied in the CD4 T cell of repeatedly immunized mice. These CD4 T cells were isolated referring to CD45RB, CD27 and CD122 markers, and fractionated cells were adoptively transferred into naïve recipients. Autoantibodies in sera of recipient mice were measured 2 weeks after cell transfer. Further, we performed microarray analysis (Whole Mouse Genome Microarray; Agilent Technologies) to investigate gene expression of CD45RB^lo122^lo CD4 T cell, and flow cytometry of CD45RB^lo122^lo CD4 T cell to study protein expression profiles of aiCD4 T cell in the mice immunized 12x with OVA. 

Results: Upon repeated immunization 12x with OVA, KLH or SEB, varieties of autoantibodies including RF, anti-Sm and anti-dsDNA antibodies were generated. Simultaneously, CD45RB^lo, CD27^lo and CD122^hi CD4 T cells were significantly expanded as compared with control mice upon repeated immunization with either OVA, KLH or SEB. Adoptive transfer of fractionated CD4 T cells with either CD45RB, CD27 or CD122 markers of the mice immunized 12x with OVA showed that both CD45RB^lo CD4 T cell and CD122^lo CD4 T cells were capable of inducing autoantibodies in the naïve recipients. However, CD27 marker was irrelevant for inducing autoantibodies. Consequently, we transferred CD45RB^lo122^lo CD4 T cells into naïve mice and found that both RF and anti-dsDNA antibody were indeed significantly increased. In microarray analyses, we compared the gene expression profile between CD45RB^lo122^lo CD4 T cell and the rest of CD4 T cell subsets after immunization 12x with OVA. We found that chemokine (C-C motif) receptor 4 (Ccr4) was increased x4 in the CD45RB^lo122^lo CD4 subsets. Surface expression of CCR4 protein was also similarly significantly increased in this subset.

Conclusion:  The aiCD4 T cell that induces SLE belongs to a CCR4⁺CD45RB^lo122^lo CD4 subpopulation.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-autoantibody-inducing-cd4-t-cell-aicd4-t-cell-belongs-to-ccr4cd45rblo122lo-cd4-subpopulation-a-novel-self-organized-criticality-theory-explains-the-cause-of-systemic-lup/