The Th2-response in mercuric chloride-induced autoimmunity requires continuing costimulation via CD28

B7-2/CD28 costimulatory pathway in children with atopic dermatitis and its connection with immunoglobulin E, intracellular interleukin-4 and interferon-gamma production by T cells during a 1-month follow-up

BACKGROUND

The best defined costimulators for activation of T lymphocytes are B7-1 and B7-2 on antigen presenting cells (APC) that bind to CD28 on T cells. Several studies showed that CD28 is critical for type 2 T helper cells (Th2) inflammation and depends mainly on the interaction of CD28 with B7-2. Some authors suggested a role for B7-2 B cells in immunoglobulin E (IgE) synthesis.

OBJECTIVE

We decided to study B7-2/CD28 interaction in atopic dermatitis (AD) and correlations with total and specific IgE, intracellular interleukin 4-(IL-4) and interferon-gamma (IFN-gamma) production during a 1-month follow-up.

METHODS

We studied 24 AD children with allergy to cow's milk. Lymphocyte subsets (B7-2 on B cells, CD28(+) on T cells, IL-4 and IFN-gamma producing T helper cells), total and specific IgE, and IgG4 at days 1 and 30 were also studied. Scoring of atopic dermatitis (SCORAD) significantly decreased.

RESULTS

CD28(+)/CD3(+)/CD57 correlated with B7-2 B cells at days 1 and 30, with IL-4 and IFN-gamma producing T helper cells at day 1 and with SCORAD at day 30. B7-2 B cells negatively correlated with IgE at day 30. Percentage of B7-2 B cells negatively correlated with total and specific IgE at day 30.

CONCLUSION

Our results support the importance of CD28/B7 costimulation in AD children and the relation of CD28 with Th1 and Th2 cytokines. However, our results do not confirm the hypothesis about the preferential role of B7-2 in Th2 activation and IgE synthesis. It could raise a question about B7-2 blockade efficacy in AD children. Further investigations on B7 family members and their functions could help to distinguish target for more clinically efficient B7/CD28 blockage in AD.

Autoantibodies against CD28 are associated with atopic diseases

The B7-1/B7-2-CD28/CTLA-4 pathway is crucial in regulating T cell activation and tolerance. Autoantibodies to surface molecules on lymphocytes have already been described in various immune conditions, such as autoimmune diseases, infections and blood transfusions. The objective of this study was to test sera from healthy individuals and from patients for association of CD28 autoantibodies with inflammatory and non-inflammatory diseases. First, CD28 was obtained by digestion of CD28-Ig fusion protein with trypsin. The cleavage products were separated by sodium dodecyl sulphate-page gel electrophoresis. Additionally, a CD28/GST fusion protein was expressed in Escherichia coli and was used to establish an enzyme-linked immunosorbent assay for detection of autoantibodies against CD28. Sera from healthy individuals (n = 72) and patients with different inflammatory and non-inflammatory skin diseases (n = 196) were tested for the presence of autoantibodies against CD28. Using mixed lymphocyte reaction (MLR), purified autoantibodies against CD28 were tested for their effects on CTLA-4-Ig-induced T cell anergy. In this study, for the first time, we describe the existence of autoantibodies against CD28 in humans which are associated with atopic diseases, e.g. allergic rhinitis and asthma. These antibodies stimulate T cells and overcome the CTLA-4-Ig-induced anergy of T cells in an MLR. The existence of autoantibodies against CD28, which may have a T cell-stimulating function, has been shown. The data indicate that autoantibodies against CD28 could be a new immunological mechanism in allergic inflammation. Additionally, autoantibodies against CD28 could be an important new marker to discriminate between atopic diseases and other inflammatory skin diseases.

Blockade of OX40-ligand after initial triggering of the T helper 2 response inhibits mercuric chloride-induced autoimmunity

Mercuric chloride (HgCl2)-induced autoimmunity in Brown Norway rats is a spontaneously resolving autoimmune response driven by the activation of T helper type 2 lymphocytes (Th2 cells). Treatment with antibody to OX40-ligand (OX40-L) from the time of the first HgCl2 injection for 12 days had little effect. Delayed treatment commenced 8 days after the first HgCl2 injection significantly suppressed immunoglobulin E production, splenomegaly, weight loss and mortality. This makes OX40/OX40-L signalling an attractive therapeutic target for Th2-driven autoimmune diseases. Intravenous administration of the murine antibody to OX-40-L elicited a vigorous anti-mouse immunoglobulin antibody response that was significantly enhanced compared to the response to control immunoglobulin. It is likely that this response significantly reduced the plasma half-life of the anti-OX40-L antibody and this observation has clear implications for the interpretation of data from experiments where anti-OX40-L is used in vivo.

Antineutrophil cytoplasmic autoantibodies and pathophysiology: new insights from animal models

PURPOSE OF REVIEW

Since the discovery of antineutrophil cytoplasmic autoantibodies (ANCA) and their association with the occurrence of several types of small-vessel vasculitis, a causal relation between the two has been suggested. Various in vitro and in vivo experimental data provide indirect evidence in support of this view. This article comprises a review of the animal models that have been used to investigate the pathogenesis of ANCA-associated vasculitis, and focuses on recent developments in this field.

RECENT FINDINGS

Xiao et al. provide definite proof of the pathogenic potential of ANCA in a novel mouse model of myeloperoxidase (MPO)-ANCA-associated vasculitis, in which transfer of splenocytes or IgG from MPO-/- mice immunized with murine MPO, to naive wild-type or Rag2-/- (lacking mature B and T lymphocytes) mice causes a disease remarkably similar to its human counterpart. In addition, preliminary studies by Smyth et al. show that immunization of Wistar Kyoto rats with human MPO induces antihuman MPO antibodies that cross-react with rat MPO, as well as a disease closely resembling human small-vessel vasculitis. Another murine ANCA model is the SCG/Kj mouse. A recent publication by Neumann et al., however, puts an important limitation on the use of this mouse model for the study of ANCA-associated vasculitis, demonstrating multiple immune complex deposits in the spontaneously occurring vascular lesions. SUMMARY Recently developed animal models of MPO-ANCA-associated vasculitis convincingly demonstrate that MPO-ANCA are pathogenic. Whether similar strategies can be used to develop an appropriate model for proteinase 3-ANCA-associated vasculitis remains to be investigated.