Autoimmune diseases--at the molecular level

Systemic transforming growth factor-beta in patients with bone marrow fibrosis--pathophysiological implications

Idiopathic myelofibrosis (IMF) and secondary myelofibrosis (MF) are characterized by bone marrow (BM) fibrosis, neoangiogenesis, and increased extracellular matrix (ECM) proteins. These characteristics may be partially attributed to transforming growth factor beta (TGF-beta), a cytokine produced by monocytes. In myelofibrosis, monocytes are increased and activated with concomitant up-regulation of intracytoplasmic TGF-beta. We have therefore determined systemic TGF-beta in patients with either BM fibrosis: IMF, n = 18; MF, n = 16; or without BM fibrosis: hematologic disorders with normal platelets (n = 31); high platelets (n = 9); or normal controls (n = 27). Compared with nonfibrosis sera, there was significant TGF-beta elevation in BM fibrosis sera (P < 0.0001). Most (>80%) of the TGF-beta is active and belongs to the-beta1 isoform. In situ hybridization and immunohistochemical analyses in BM biopsy sections showed a marked increase in TGF-beta1 only in patients with fibrosis. Moreover, TGF-beta protein was detected mainly in myelomonocytic-like predominant areas. To determine if another functionally similar cytokine, basic fibroblast growth factor (bFGF), may be important to BM fibrosis, we quantitated sera levels and found elevation in 57% compared with 100% elevation for TGF-beta. The data indicate that irrespective of etiology, systemic TGF-beta is elevated in patients with BM fibrosis. TGF-beta likely plays an important role in the development of BM fibrosis. The study also provides a significant parameter for early therapeutic intervention in BM fibrosis.

Modulation of integrin-mediated intercellular adhesion during the interaction of thymocytes with stromal cells expressing VLA-4 and LFA-1 ligands

Mature peripheral T cells closely regulate their intercellular interactions by modulating integrin adhesion functions. The ability of members of the integrin family to mediate intercellular adhesion is dependent on signals from within the cells (inside-out signaling) that increase the avidity of integrins for their ligands. These changes in avidity are independent of the quantitative changes on the number of receptors, and there is evidence to suggest that phosphorylation events play a predominant role in the regulation of the avidity state of the integrins. Whether such regulatory mechanisms are operative during T cell development had hitherto been an opened question. In the present work, we have used an in vitro adhesion assay between thymocytes and target cells expressing VLA-4 and LFA-1 counter ligands to determine how thymocytes can discriminate between integrin-specific signals during T cell development. Our findings are that VLA-4, but not LFA-1, is constitutively expressed in its high-avidity state during the early stages of T cell development, and that the high-avidity state of thymocytes for VCAM-1-expressing cells is closely regulated by signaling through protein kinase C and protein tyrosine kinase pathways. At later stages of development, mature thymocytes prior to leaving the thymus turn off both VLA-4 and LFA-1 adhesion functions. Our results show that the low-affinity state of integrins on peripheral mature T cells is established before mature thymocytes leave the thymus. Only when mature T cells recognize antigenic peptides in the context of major histocompatibility complex in the periphery will they turn on the adhesion function of VLA-4 and/or LFA-1 integrins.

Different T-cell activation by streptozotocin and Freund's adjuvant in popliteal lymph node (PLN)

A popliteal lymph node (PLN) test was further validated for predictive screening of autoimmunity-inducing drugs. Autoimmune-like T-cell activation of streptozotocin (STZ) was compared with the effect of Freund's complete adjuvant (FCA), injected locally into the foot pad of BALB/c mice. Early cell activation in enlarged PLN was monitored by flow cytometry. Injection of both STZ and FCA markedly increased the absolute PLN cell number as well as specific T-helper (CD4+), T-suppressor/cytotoxic (CD8+), and B (Ig+) subsets. However, quantitative analysis of early T-cell activation revealed important differences between STZ-induced PLN reaction and FCA-related lymphoproliferation. At 72 h, the number of cells stained with anti-early activation marker (EAM+; CD69+) increased over 10 times in STZ-enlarged nodes and only 3 times in the FCA-inflamed nodes. Furthermore, different cytometric profiles were noted for STZ-activated and FCA-activated cells stained with anti-interleukin-2 receptor (IL-2R) (CD25+). The data suggest the applicability of early cytometric screening of enlarged PLN for predictive analysis detection of chemicals inducing an autoimmune-like reaction.

Lymphocyte activation by liposome-trapped streptozotocin in murine popliteal lymph node (PLN) test

The lymphoproliferative potential of liposome-trapped streptoztocin (STZ) was compared to the effect of saline-dissolved STZ injected locally into the foot pad of CD-1 mice. Popliteal lymph node (PLN) enlargement and early cell activation of lymphocyte subsets were monitored during the onset of STZ-induced autoimmune-like reaction. Injection of the optimal STZ dose, 0.5 mg/foot pad, markedly increased the absolute PLN cell number as well as specific T-helper (CD4+), T-suppressor/cytotoxic (CD8+), and B-(Ig+) cell subsets stained with fluorescent monoclonal antibodies. Furthermore, there was a marked increase in the number of large/activated CD4+ and CD8+ cells and subsets bearing specific markers of early activation. These included cells stained with fluorescein-conjugated monoclonal antibodies against interleukin-2 receptor (CD25+) and early activation marker (EAM+) (CD69+), and with fluorescein-conjugated peanut agglutinin (PNA+). Surprisingly, the injection of liposome-trapped STZ, at a 1/10 of the optimal dose only, induced a marked PLN enlargement comparable to the effect of optimal STZ dose. The effect of liposome-STZ could be dissociated from the non-drug-containing MLV-related lymphocyte activation. The data suggest several possible advantages from the introduction of chemicals by the liposome route and the subsequent PLN test for chemical-induced autoimmunity. Toxicological advantages could involve better control of chemical exposure, controlled exposure to the water-insoluble substances, drastic reduction of xenobiotic dose, a stronger, clear PLN response and possible elimination or at least restriction of false-negative results, due to the liposome adjuvancity. Overall, application of liposomes as an exposure route potentialized the STZ-induced early lymphocyte activation.

Pathogenic anti-DNA idiotype-reactive IgG in intravenous immunoglobulin preparations

This study was addressed to explore the reactivity of natural anti-idiotypes from commercial lots of immunoglobulins to several idiotypes (Ids), usually expressed by anti-DNA molecules in lupus nephritis. Eleven intravenous immunoglobulin (IVIG) preparations and nine (three polyvalent and six hyper-immune) intramuscular IgG were investigated for specific content of anti-DNA, anti-F(ab')2 and antibodies reacting with several anti-DNA IgG Ids. Two samples (nos 6 and 11) showed high reactivity with allogeneic F(ab')2 and with F(ab')2 of myeloma proteins bearing the anti-DNA Id 3I+ and the 8.12+. Since both 3I and 8.12 Id markers are known to characterize pathogenic anti-DNA IgG in systemic lupus erythematosus (SLE), anti-Id antibodies to these markers were obtained by absorbing the IVIG samples nos 6 and 11 to Sepharose columns coupled with pooled F(ab')2 fragments of 3I(+)-F4(+)-8.12(+)-myeloma proteins. Inhibition experiments showed that anti-8.12 Id-eluted IgG induced a selective suppression of the DNA-reactive antibodies derived from patients with active lupus nephritis to their substrate, suggesting the involvement of 8.12+ molecules in the SLE glomerular damage. Since 8.12+ anti-DNA are nephritogenic antibodies, the occurrence of anti-8.12+ Id in commercial IVIG may be of potential therapeutic relevance in modulating the pathogenic SLE Id network. Previous variable results of IVIG treatment in SLE, such as resolution of proteinuria or worsening nephritis, could be related to variable enrichment of different lots of IVIG in suppressive anti-pathogenic Id antibodies.