Humanized mice as a model for aberrant responses in human T cell immunotherapy.

Immune-deficient mice, reconstituted with human stem cells, have been used to analyze human immune responses in vivo. Although they have been used to study immune responses to xenografts, allografts, and pathogens, there have not been models of autoimmune disease in which the mechanisms of the pathologic process can be analyzed. We have found that reconstituted "humanized" mice treated with anti-CTLA-4 Ab (ipilimumab) develop autoimmune disease characterized by hepatitis, adrenalitis, sialitis, anti-nuclear Abs, and weight loss. Induction of autoimmunity involved activation of T cells and cytokine production, and increased infiltration of APCs. When anti-CTLA-4 mAb-treated mice were cotreated with anti-CD3 mAb (teplizumab), hepatitis and anti-nuclear Abs were no longer seen and weight loss did not occur. The anti-CD3 blocked proliferation and activation of T cells, release of IFN-γ and TNF, macrophage infiltration, and release of IP-10 that was induced with anti-CTLA-4 mAb. We also found increased levels of T regulatory cells (CD25(+)CD127(-)) in the spleen and mesenteric lymph nodes in the mice treated with both Abs and greater constitutive phosphorylation of STAT5 in T regulatory cells in spleen cells compared with mice treated with anti-CTLA-4 mAb alone. We describe a model of human autoimmune disease in vivo. Humanized mice may be useful for understanding the mechanisms of biologics that are used in patients. Hepatitis, lymphadenopathy, and other inflammatory sequelae are adverse effects of ipilimumab treatment in humans, and this study may provide insights into this pathogenesis and the effects of immunologics on autoimmunity.

Autoantigens: novel forms and presentation to the immune system.

It is clear that lupus autoimmunity is marked by a variety of abnormalities, including those found at a macroscopic scale, cells and tissues, as well as more microenvironmental influences, originating at the individual cell surface through to the nucleus. The convergence of genetic, epigenetic, and perhaps environmental influences all lead to the overt clinical expression of disease, reflected by the presences of autoantibodies and tissue pathology. This review will address several specific areas that fall among the non-genetic factors that contribute to lupus autoimmunity and related syndromes. In particular, we will discuss the importance of understanding various protein post-translational modifications (PTMs), mechanisms that mediate the ability of "modified self" to trigger autoimmunity, and how these PTMs influence lupus diagnosis. Finally, we will discuss altered pathways of autoantigen presentation that may contribute to the perpetuation of chronic autoimmune disease.

Transfer of antigen from human B cells to dendritic cells.

The cooperation of B lymphocytes with other antigen presenting cells (APCs) is often necessary in the efficient processing and presentation of antigen. Herein, we describe a mechanism by which B cells physically interact with dendritic cells (DCs) resulting in the transfer of B cell receptor (BCR)-enriched antigen to these APCs. Antigen transfer involves direct contact between the two cells followed by the capture of B cell derived membrane and intracellular components. Strikingly, DCs acquire greater amounts of antigen by transfer from B cells than by endocytosis of free antigen. Blocking scavenger receptor A, a DC surface receptor involved in membrane acquisition, abrogates these events. We propose that antigen transfer from B cells to DCs results in a more focused immunologic response due to the selective editing of Ag by the BCR.

Inhibition of antigen trafficking through scavenger receptor A.

B cell acquisition and presentation of specific autoantigens (auto-Ags) are thought to play an important and complex role in autoimmunity development. We previously identified scavenger receptor A (SR-A) as an early target in altering B cell-mediated autoimmunity. SR-A is highly expressed on professional antigen-presenting cells such as macrophages (MΦs) and dendritic cells (DCs). In this study, we demonstrate that SR-A is responsible for controlling B cell interactions with DCs/MΦs to promote Ag transfer from B cells to DCs/MΦs. We established a high-throughput ELISA-based screen to identify novel SR-A inhibitors, the specificity of which was determined by dose dependence and Biacore surface plasmon resonance testing. We identified small molecule inhibitors (SMIs) able to reduce SR-A-mediated Ag transfer in human cells. In particular, the SMIs prevented SR-A-positive cells from accumulating/loading Ag over time. Furthermore, we determined that one SMI, sennoside B, can reduce SR-A-mediated capture of B cells. Finally, SMI-mediated decreases in Ag transfer or accumulation reduced T cell proliferation in vitro and in vivo. These observations demonstrate that B cell-DC/MΦ interactions are conducive to promoting Ag trafficking between these cell types via SR-A. Inhibitors of SR-A may provide a novel therapeutic strategy in ameliorating autoimmune disease development.