Disparate effects of depletion of CD1d-reactive T cells during early versus late stages of disease in a genetically susceptible model of lupus

Abstract

Some T cells react with lipid antigens bound to antigen-presenting molecule CD1d. Numbers and functions of a subset of such lipid-reactive T cells are reduced in patients with systemic lupus erythematosus (SLE) and their relatives, as well as in genetically susceptible and chemically induced animal models of lupus-like disease. We have reported that the germline deletion of CD1d exacerbates lupus, suggesting a protective role of these cells in the development of lupus. The use of a knockout mouse model in this study, however, did not allow examination of the role of these cells at different stages of disease. Here, we describe an approach to deplete CD1d-dependent T cells, which allowed us to investigate the role of these cells at different stages of disease in genetically lupus-prone NZB/NZW F1 (BWF1) mice. Repeated intravenous injections of large numbers of CD1d-transfected cells resulted in ∼50-75% reduction in these cells, as defined by the expression of CD4, NK1.1 and CD122, and lack of expression of CD62 ligand. TCR γδ (+)NK1.1(+) cells were also reduced in the recipients of CD1d-transfected cells as compared with control recipients. Such depletion of CD1d-reactive T cells in preclinical BWF1 mice resulted in disease acceleration with a significant increase in proteinuria and mortality. In older BWF1 mice having advanced nephritis, however, such depletion of CD1d-reactive T cells resulted in some disease improvement. Taken together, these data as well as our published studies suggest that CD1d-reactive T cells protect against the development of lupus in animal models. However, these cells appear to be unable to suppress established lupus nephritis in these animals, and might even play a disease aggravating role in late stages of disease.

Figure 1

Effect of in vivo transfer of CD1d-expressing cells on natural killer T-cell numbers. BWF1 mice received i.v. injections of irradiated CD1d-transfected A20 cells (50 million) twice a week. Control mice received irradiated untransfected 50 million A20 cells. (a) Expression of CD1d on transfected A20 cells. (b) Seven days after the second injection, five mice in each group were sacrificed to harvest spleens. Pooled spleen cells were subjected to red blood cell lysis followed by depletion of I–A^d+I–E^d+ and CD11b⁺ cells using magnetic cell separation. The negatively selected cell fraction consisting of >90% T cells were analyzed for natural killer T cells by flow cytometry. Numbers on dotplots represent the frequency of NK1.1⁺ cells as percentages of T cells.

Figure 2

Effect of in vivo transfer of CD1d-expressing cells on proteinuria and survival. BWF1 mice were injected i.v. with CD1d-transfected A20 cells (0.5 or 50 million) or saline as indicated in the figure twice a week for 6 weeks (n=10 mice per group). Control mice received saline or irradiated untransfected 50 million A20 cells (n=15 mice per group). Results are shown severe as % mice with proteinuria (defined as±300 mg/dl on two consecutive examinations) and as % cumulative mortality. (a, b) Young (12-week-old), pre-nephritic BWF1 mice. *p < 0.01, high-dose transfected cell recipients vs. saline or untransfected cell recipients, log-rank test. (c, d) Diseased, 22–24-week-old BWF1 mice that already had moderate proteinuria. *p < 0.05, high-dose transfected cell group vs. other three groups at 29–33 weeks of age, Fisher's exact test. Results are from one representative of three independent experiments.