In vivo and in vitro death of mature T cells induced by separate signals to CD4 and alpha beta TCR

Cultured circulating tumor cells and their derived xenografts for personalized oncology

Recent cancer research has demonstrated the existence of circulating tumor cells (CTCs) in cancer patient's blood. Once identified, CTC biomarkers will be invaluable tools for clinical diagnosis, prognosis and treatment. In this review, we propose ex vivo culture as a rational strategy for large scale amplification of the limited numbers of CTCs from a patient sample, to derive enough CTCs for accurate and reproducible characterization of the biophysical, biochemical, gene expressional and behavioral properties of the harvested cells. Because of tumor cell heterogeneity, it is important to amplify all the CTCs in a blood sample for a comprehensive understanding of their role in cancer metastasis. By analyzing critical steps and technical issues in ex vivo CTC culture, we developed a cost-effective and reproducible protocol directly culturing whole peripheral blood mononuclear cells, relying on an assumed survival advantage in CTCs and CTC-like cells over the normal cells to amplify this specified cluster of cancer cells.

Slipping through the Cracks: Linking Low Immune Function and Intestinal Bacterial Imbalance to the Etiology of Rheumatoid Arthritis

Autoimmune diseases (ADs) are considered to be caused by the host immune system which attacks and destroys its own tissue by mistake. A widely accepted hypothesis to explain the pathogenic mechanism of ADs is “molecular mimicry,” which states that antibodies against an infectious agent cross-react with a self-antigen sharing an identical or similar antigenic epitope. However, this hypothesis was most likely established based on misleading antibody assay data largely influenced by intense false positive reactions involved in immunoassay systems. Thus reinvestigation of this hypothesis using an appropriate blocking agent capable of eliminating all types of nonspecific reactions and proper assay design is strongly encouraged. In this review, we discuss the possibility that low immune function may be the fundamental, common defect in ADs, which increases the susceptibility to potential disease causative pathogens located in the gastrointestinal tract (GI), such as bacteria and their components or dietary components. In addition to these exogenous agents, aberrations in the host's physical condition may disrupt the host defense system, which is tightly orchestrated by “immune function,” “mucosal barrier function,” and “intestinal bacterial balance.” These disturbances may initiate a downward spiral, which can lead to chronic health problems that will evolve to an autoimmune disorder.

Different types of cell death induced by enterotoxins

The infection of bacterial organisms generally causes cell death to facilitate microbial invasion and immune escape, both of which are involved in the pathogenesis of infectious diseases. In addition to the intercellular infectious processes, pathogen-produced/secreted enterotoxins (mostly exotoxins) are the major weapons that kill host cells and cause diseases by inducing different types of cell death, particularly apoptosis and necrosis. Blocking these enterotoxins with synthetic drugs and vaccines is important for treating patients with infectious diseases. Studies of enterotoxin-induced apoptotic and necrotic mechanisms have helped us to create efficient strategies to use against these well-characterized cytopathic toxins. In this article, we review the induction of the different types of cell death from various bacterial enterotoxins, such as staphylococcal enterotoxin B, staphylococcal alpha-toxin, Panton-Valentine leukocidin, alpha-hemolysin of Escherichia coli, Shiga toxins, cytotoxic necrotizing factor 1, heat-labile enterotoxins, and the cholera toxin, Vibrio cholerae. In addition, necrosis caused by pore-forming toxins, apoptotic signaling through cross-talk pathways involving mitochondrial damage, endoplasmic reticulum stress, and lysosomal injury is discussed.

Protection from experimental autoimmune encephalomyelitis (EAE): non-depleting anti-CD4 mAb treatment induces peripheral T-cell tolerance to MBP in PL/J mice

Following pre-treatment with a non-depleting anti-CD4 mAb (H129.19) that produces long-lasting receptor saturation, PL/J mice were fully protected from experimental auto-immune encephalomyelitis (EAE) induced by injection of myelin basic protein (MBP). These mice did not develop EAE following MBP re-challenge 5-10 weeks later when the CD4+ cells were no longer coated by the mAb and their lymph node cells were specifically unresponsive to MBP stimulation in vitro. Moreover, superantigen staphylococcal enterotoxin B (SEB) inoculation, which re-induces EAE in MBP immunized mice, failed to activate encephalitogenic T-cells in anti-CD4 + MBP treated mice, even after MBP re-challenge, indicating that tolerance in the peripheral T-cell compartment was achieved. However, MBP re-challenge 16 weeks later, but not SEB, produced an acute episode of EAE in these mice, while it failed to induce disease in a parallel group of adult thymectomized mice. These results indicate that no memory of the first priming exists at this time and that new MBP-specific T-cell precursors are peripheralized and produce EAE after MBP recognition.

Treatment with a chimeric CD4 monoclonal antibody is associated with a relative loss of CD4+/CD45RA+ cells in patients with rheumatoid arthritis

This study investigates immunogenicity and in vivo effects on T-cells of long-term CD4 monoclonal antibody treatment of patients with rheumatoid arthritis. Patients were treated with several dosage regimens of a chimeric CD4 monoclonal antibody entitled cM-T412 over the course of 1 year. The circulating CD4+ T-cell count sharply decreased after the first cM-T412 injection and slowly recovered after the last injection. Within the CD4+ subset there was a selective depletion of CD45RA+ T cells, HLA-DR+, and CD25+ cells, providing evidence that activated/memory CD4+ cells resist the effect of CD4 monoclonal antibodies. Studies on cytokine production by peripheral blood mononuclear cells cultures in vitro revealed no differential effect on the production of interleukin-4 compared to interferon-gamma, indicating that a shift from a Th1 to a Th2 lymphokine production profile was not achieved. Human anti-monoclonal antibodies (HAMA) were induced in a minority of the patients predominantly after the first treatment course. All the sera containing HAMA specifically inhibited the binding of cM-T412 to T-cells. However, HAMA formation does not interfere with the biological effect of repeated cM-T412 administration since the degree of CD4 depletion following repeated administration of cM-T412 to patients with and without blocking antibodies was similar. We conclude that the currently available data are of critical importance in the interpretation of the obtained clinical experience and for further development of this therapeutic strategy.

Induction of donor specific transplantation tolerance to cardiac allografts following treatment with nondepleting (RIB 5/2) or depleting (OX-38) anti-CD4 mAb plus intrathymic or intravenous donor alloantigen

The nondepleting monoclonal antirat CD4 antibody, RIB 5/2, has been shown to modulate, but not eliminate, the CD4+ T cells and to prolong survival of rat skin, renal, or cardiac allografts when serially administered after transplantation. In the present study, we compared the efficacy of recipient pretreatment with a single dose of nondepleting RIB 5/2 or depleting OX-38 anti-CD4 monoclonal antibody plus donor alloantigen given intravenously or intrathymically 21 days before transplantation on the survival of completely MHC-mismatched rat cardiac allografts. Intraperitoneal injection of a single dose (20 mg/kg) of RIB 5/2 resulted in a decrease in CD4 surface molecule expression on peripheral CD4+ T cells without cell elimination as shown by FACS analysis. The nonspecific effect of a single dose of RIB 5/2 mAb had resolved by 21 days after treatment as evidenced by the almost complete recovery of normal surface CD4 molecule expression. Cardiac allografts transplanted immediately or 21 days after a single dose of RIB 5/2 alone were uniformly acutely rejected. On the other hand, recipients treated with depleting anti-CD4 OX-38 (20 mg/kg) acutely rejected cardiac allografts transplanted 21 days later, but indefinitely accepted all grafts transplanted on the same day. In contrast, combined treatment with i.v. donor splenocytes (25 x 10(6)) plus nondepleting RIB 5/2, but not with depleting anti-CD4 mAb, OX-38, resulted in survival for more than 100 days in 75% of recipients of donor specific, but not third party, cardiac allografts transplanted 21 days later. Irradiation (3000 rads) of the i.v. donor splenocytes combined with RIB 5/2 abrogated their tolerizing effect. When donor antigen was given intrathymically, both RIB 5/2 and OX-38 resulted in indefinite tolerance to cardiac allografts transplanted 21 days later. The failure of exogenous administration of high dose (180,000 IU/injection) rIL-2 for 10 days to reverse the unresponsiveness of i.v. SC plus RIB 5/2 pretreatment suggests that this tolerant state is not due to a deficiency of IL-2. In vitro studies showed marked inhibition of MLC responsiveness and cytolytic T cell activity in tolerant recipients that cannot be reversed by the addition of IL-2. Thus, pretransplant intravenous donor alloantigen combined with a dose of nondepleting anti-CD4 mAb, RIB 5/2, which alone has no significant effect, induced donor specific cardiac allograft tolerance.

Apoptosis without decrease of cell DNA content

Apoptosis of human B cells and murine T and B cells was analyzed by DNA agarose gel electrophoresis, clamped homogeneous electric field, measurement of cell DNA content by flow cytometry, transmission electron microscopy and by UV microscopy. Apoptosis was induced by etoposide (an inhibitor of topoisomerase II), by the calcium ionophore ionomycin or by cross-linking of membrane immunoglobulins (Ig) with anti-Ig-antibodies. Two types of apoptosis could be defined. Apoptosis resulting in small DNA fragments (180-200 base pairs and multiples thereof) was associated with a typical 'ladder' in agarose gel electrophoresis and a decrease in cell DNA content assessed by flow cytometry. Conversely apoptosis with large DNA fragments (100-150 kilobase pairs) was only demonstrated by clamped homogeneous electric field but was not associated with decreased cell DNA content or the observation of DNA ladders. Nuclear condensation without fragmentation was more frequent when apoptosis generated large DNA fragments. The type of apoptosis appears to be an intrinsic property of each cell type.