Approximately 10% of peripheral CD4+ cells and less than 1% of CD8+ cells in normal unimmunized adult mice express the IL-2 receptor alpha-chain (CD25) molecules. When CD4+ cell suspensions prepared from BALB/c nu/+ mice lymph nodes and spleens were depleted of CD25+ cells by specific mAb and C, and then inoculated into BALB/c athymic nude (nu/nu) mice, all recipients spontaneously developed histologically and serologically evident autoimmune diseases (such as thyroiditis, gastritis, insulitis, sialoadenitis, adrenalitis, oophoritis, glomerulonephritis, and polyarthritis); some mice also developed graft-vs-host-like wasting disease. Reconstitution of CD4+CD25+ cells within a limited period after transfer of CD4+CD25- cells prevented these autoimmune developments in a dose-dependent fashion, whereas the reconstitution several days later, or inoculation of an equivalent dose of CD8+ cells, was far less efficient for the prevention. When nu/nu mice were transplanted with allogeneic skins or immunized with xenogeneic proteins at the time of CD25- cell inoculation, they showed significantly heightened immune responses to the skins or proteins, and reconstitution of CD4+CD25+ cells normalized the responses. Taken together, these results indicate that CD4+CD25+ cells contribute to maintaining self-tolerance by down-regulating immune response to self and non-self Ags in an Ag-nonspecific manner, presumably at the T cell activation stage; elimination/reduction of CD4+CD25+ cells relieves this general suppression, thereby not only enhancing immune responses to non-self Ags, but also eliciting autoimmune responses to certain self-Ags. Abnormality of this T cell-mediated mechanism of peripheral tolerance can be a possible cause of various autoimmune diseases.

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Immunologic self-tolerance maintained by activated T cells expressing IL-2 receptor alpha-chains (CD25). Breakdown of a single mechanism of self-tolerance causes various autoimmune diseases.

Through the study of transcriptional activation in response to interferon alpha (IFN-alpha) and interferon gamma (IFN-gamma), a previously unrecognized direct signal transduction pathway to the nucleus has been uncovered: IFN-receptor interaction at the cell surface leads to the activation of kinases of the Jak family that then phosphorylate substrate proteins called STATs (signal transducers and activators of transcription). The phosphorylated STAT proteins move to the nucleus, bind specific DNA elements, and direct transcription. Recognition of the molecules involved in the IFN-alpha and IFN-gamma pathway has led to discoveries that a number of STAT family members exist and that other polypeptide ligands also use the Jak-STAT molecules in signal transduction.

https://science.sciencemag.org/content/sci/264/5164/1415.full.pdf

Jak-STAT pathways and transcriptional activation in response to IFNs and other extracellular signaling proteins

Rapid colorimetric assay for cell growth and survival. Modifications to the tetrazolium dye procedure giving improved sensitivity and reliability.

Oncology Meets Immunology: The Cancer-Immunity Cycle

SUMMARY The availability of an increasing number of antiretroviral agents and the rapid evolution of new information has introduced extraordinary complexity into the treatment of HIV-infected persons. In 1996, the Department of Health and Human Services and the Henry J. Kaiser Family Foundation convened the Panel on Clinical Practices for the Treatment of HIV to develop guidelines for the clinical management of HIV-infected adults and adolescents. This report recommends that care should be supervised by an expert, and makes recommendations for laboratory monitoring including plasma HIV RNA, CD4 cell counts and HIV drug resistance testing. The report also provides guidelines for antiretroviral therapy, including when to start treatment, what drugs to initiate, when to change therapy, and therapeutic options when changing therapy. Special considerations are provided for adolescents and pregnant women. As with treatment of other chronic conditions, therapeutic decisions require a mutual understanding between the patient and the health care provider regarding the benefits and risks of treatment. Antiretroviral regimens are complex, have major side effects, pose difficulty with adherence, and carry serious potential consequences from the development of viral resistance due to non-adherence to the drug regimen or suboptimal levels of antiretroviral agents. Patient education and involvement in therapeutic

/pdf/guidelines-for-the-use-of-antiretroviral-agents-in-hiv-3wuv1pwax4.pdf

Guidelines for the use of antiretroviral agents in HIV-infected adults and adolescents

Several soluble factors have recently been associated with the proliferation and differentiation of thymus-derived lymphocytes. One of these factors present in medium conditioned by T cell mitogen-stimulated lymphocytes has the ability to promote the long-term culture of normal and antigen-specific cytotoxic T cells. We report a method to test for this proliferative stimulus in the form of a sensitive microassay based upon the tritiated thymidine incorporation of continuous murine tumorspecific cytotoxic T cell lines (CTLL). The microassay requires microliter quantities of sample fluid and is amenable to quantitative analysis. This highly reproducible, quantitative assay for T cell growth factor (TCGF) has allowed investigation as to the kinetics of TCGF generation and has revealed that T lymphocytes are required for its production. Further investigation has supported the notion that this nonspecies-specific factor is actively removed from tissue culture medium by the proliferation of either T cell mitogen-activated lymphocytes or CTLL.

T Cell Growth Factor: Parameters of Production and a Quantitative Microassay for Activity

Interleukin-2 (IL-2), the first of a series of lymphocytotrophic hormones to be recognized and completely characterized, is pivotal for the generation and regulation of the immune response. A T lymphocyte product, IL-2 also stimulates T cells to undergo cell cycle progression via a finite number of interactions with its specific membrane receptors. Because T cell clonal proliferation after antigen challenge is obligatory for immune responsiveness and immune memory, the IL-2-T cell system has opened the way to a molecular understanding of phenomena that are fundamental to biology, immunology, and medicine.

https://science.sciencemag.org/content/sci/240/4856/1169.full.pdf

Interleukin-2: inception, impact, and implications.

Combination therapy for HIV-1 infection can reduce plasma virus to undetectable levels, indicating that prolonged treatment might eradicate the infection. However, HIV-1 can persist in a latent form in resting CD4+ T cells. We measured the decay rate of this latent reservoir in 34 treated adults whose plasma virus levels were undetectable. The mean half-life of the latent reservoir was very long (43.9 months). If the latent reservoir consists of only 1 x 10(5) cells, eradication could take as long as 60 years. Thus, latent infection of resting CD4+ T cells provides a mechanism for lifelong persistence of HIV-1, even in patients on effective anti-retroviral therapy.

Latent infection of CD4 + T cells provides a mechanism for lifelong persistence of HIV-1, even in patients on effective combination therapy

MANY investigators have been successful in the maintenance of long term tissue culture of human bone marrow-derived (B) cells. These cell lines have been established from both normal subjects1 and from patients with lymphoproliferative disorders2. In most cases, long term B-cell lines have been shown to harbour the Epstein–Barr virus genome which some investigators feel is required for establishment and maintenance of long-term cultures3. There are fewer reports describing continuous culture of human thymus derived (T) cell lines, and when successful, the lines have only been established from patients with acute lymphocytic leukaemia4. Although these cell lines have been shown to bear surface markers of normal human T lymphocytes, there have been no reports which suggest that they possess the ability to respond to immunologic stimuli or to differentiate into antigen-specific lymphocytes. Cytotoxic murine T cells have been kept in continuous culture only through repetitive mixed-lymphocyte stimulation5. In contrast to long term human lymphocyte lines, these cells proliferated only when stimulated with allogeneic lymphocytes and eventually died after a few weeks in culture. Morgan, Ruscetti and Gallo recently reported a method by which medium conditioned by phytohaemagglutinin-stimulated normal human lymphocytes allowed for the selective long-term growth of normal T cells6. In contrast to the previously mentioned cell lines, the proliferation of these reported T-cell cultures was totally dependent on the presence of an exogenously-produced growth factor supplied by the conditioned medium. In this report we describe an adaptation of this method which allows the long term culture of antigen-selected cytotoxic T cells which continue to demonstrate high levels of syngeneic tumour-specific cytotoxicity after more than 4 months in culture.

Long term culture of tumour-specific cytotoxic T cells.

We have examined the mechanism of thalidomide inhibition of lipopolysaccharide (LPS)-induced tumor necrosis factor alpha (TNF-alpha) production and found that the drug enhances the degradation of TNF-alpha mRNA. Thus, the half-life of the molecule was reduced from approximately 30 to approximately 17 min in the presence of 50 micrograms/ml of thalidomide. Inhibition of TNF-alpha production was selective, as other LPS-induced monocyte cytokines were unaffected. Pentoxifylline and dexamethasone, two other inhibitors of TNF-alpha production, are known to exert their effects by means of different mechanisms, suggesting that the three agents inhibit TNF-alpha synthesis at distinct points of the cytokine biosynthetic pathway. These observations provide an explanation for the synergistic effects of these drugs. The selective inhibition of TNF-alpha production makes thalidomide an ideal candidate for the treatment of inflammatory conditions where TNF-alpha-induced toxicities are observed and where immunity must remain intact.

/pdf/thalidomide-exerts-its-inhibitory-action-on-tumor-necrosis-1oahsmtbt0.pdf

Kendall A. Smith

Papers

T Cell Growth Factor: Parameters of Production and a Quantitative Microassay for Activity

Interleukin-2: inception, impact, and implications.

Latent infection of CD4 + T cells provides a mechanism for lifelong persistence of HIV-1, even in patients on effective combination therapy

Long term culture of tumour-specific cytotoxic T cells.

Thalidomide exerts its inhibitory action on tumor necrosis factor alpha by enhancing mRNA degradation.