José Mengel

Summary: The role of natural killer (NK) T cells in the development of lupus‐like disease in mice is still controversial. We treated NZB/W mice with anti‐NK1.1 monoclonal antibodies (mAbs) and our results revealed that administration of either an irrelevant immunoglobulin G2a (IgG2a) mAb or an IgG2a anti‐NK1.1 mAb increased the production of anti‐dsDNA antibodies in young NZB/W mice. However, the continuous administration of an anti‐NK1.1 mAb protected aged NZB/W mice from glomerular injury, leading to prolonged survival and stabilization of the proteinuria. Conversely, the administration of the control IgG2a mAb led to an aggravation of the lupus‐like disease. Augmented titres of anti‐dsDNA in NZB/W mice, upon IgG2a administration, correlated with the production of BAFF/BLyS by dendritic, B and T cells. Treatment with an anti‐NK1.1 mAb reduced the levels of interleukin‐16, produced by T cells, in spleen cell culture supernatants from aged NZB/W. Adoptive transfer of NK T cells from aged to young NZB/W accelerated the production of anti‐dsDNA in recipient NZB/W mice, suggesting that NK T cells from aged NZB/W are endowed with a B‐cell helper activity. In vitro studies, using purified NK T cells from aged NZB/W, showed that these cells provided helper B‐cell activity for the production of anti‐dsDNA. We concluded that NK T cells are involved in the progression of lupus‐like disease in mature NZB/W mice and that immunoglobulin of the IgG2a isotype has an enhancing effect on antibody synthesis due to the induction of BAFF/BLyS, and therefore have a deleterious effect in the NZB/W mouse physiology.

This study evaluated the regulatory function of NK1.1+ cells during Trypanosoma cruzi infection. Both thymectomized (Tx C57Bl/6) and euthymic C57Bl/6 mice (C57Bl/6) were infected intraperitoneally with the Tulahuen strain. NK1.1+ cells were depleted in vivo by anti-NK1.1 mAb. Spleen cells were analyzed by flow cytometry for the expression of CD44 and CD69 on T cells. Supernatants from splenocytes were used to measure nitrite concentration (quantified by Griess reagent). Interleukin 2 and IFN-gamma levels were determined by ELISA. The protocols used herein were approved by the Institutional Committee for Ethics. Student's t or Kruskal-Wallis tests were applied, as indicated. The number of T cells expressing CD69 increased progressively during T. cruzi infection in NK1.1 cell-depleted C57Bl/6 mice. In spite of an increased early T cell activation during infection, the percentage of CD4+ CD44high T cells did not augment in NK1.1 cell-depleted C57Bl/6 mice compared with untreated C57Bl/6 controls. Serum levels of IFN-gamma in anti-NK1.1-treated mice were higher than in non-depleted animals. Con-A-stimulated spleen cell supernatants from NK1.1 cell-depleted animals contained increased levels of IL-2 and nitric oxide (NO) during early infection. After the first week of infection, NO overproduction and high levels of IFN-gamma in anti-NK1.1-tre-ated C57Bl/6 mice appeared to be related to susceptibility and hyperactivation of peripheral T cells. Finally, this study suggests a novel regulatory function of NK1.1+ cells during T. cruzi infection. Without NK1.1 cells, T lymphocytes are hyperactivated but do not differentiate to effector/memory T cells in infected C57Bl/6 mice.