Differential effect of neonatal thymectomy on systemic and organ-specific autoimmune disease

Thymectomy on day 3 after birth (d3tx) depletes CD4+CD25+ regulatory T cells leading to multiple independent organ-specific autoimmune diseases. However, systemic autoimmune disease such as systemic lupus erythematosus has not been reported in d3tx mice. Herein, we investigate the effect of d3tx on spontaneous autoantibody response and immune complex glomerulonephritis (GN) in the lupus-prone (SWR x NZB)F1 (SNF1) mice. The d3tx SNF1 mice developed accelerated antibody responses to double-stranded DNA and DNA-histone complexes, and an increased frequency of activated CD4+ T cells. Unexpectedly, the renal histopathology and mortality from GN were significantly ameliorated in d3tx SNF1 mice, which concomitantly exhibited a Th2-biased antibody response. By 16 weeks, the d3tx mice had higher levels of total and autoantigen-specific IgG1, and at 12 months, the autoantigen-specific IgG2a was significantly below that of the sham thymectomized mice. These differences corresponded with reduction in total and autoantigen-specific IgG2a in the renal eluates of the d3tx mice. In addition, while all the mice had immune complex deposition in the mesangium and peripheral capillary loops of the glomeruli, IgG2a and C3 deposits restricted to the mesangial regions alone were more frequent in d3tx mice. D3tx SNF1 mice, protected from lupus-like GN, developed organ-specific autoimmune responses and diseases including prostatitis, orchitis and oophoritis, and antibodies to prostate, cardiac and skeletal muscle antigens. Therefore, d3tx paradoxically protects SNF1 mice from genetically prone lupus-like GN, yet promotes de novo organ-specific autoimmunity.