Autoimmunity, immunodeficiency and mucosal infections: chronic intestinal inflammation as a sensitive indicator of immunoregulatory defects in response to normal luminal microflora

Despite the fact that target antigens and the genetic basis of several autoimmune diseases are now better understood, the initial events leading to a loss of tolerance towards self-components remain unknown. One of the most attractive explanations for autoimmune phenomena involves various infections as possible natural events capable of initiating the process in genetically predisposed individuals. The most accepted explanation of how infection causes autoimmunity is based on the concept of "molecular mimicry" (similarity between the epitopes of an autoantigen and the epitopes in the environmental antigen). Infectious stimuli may also participate in the development of autoimmunity by inducing an increased expression of stress proteins (hsp), chaperones and transplantation antigens, which leads to abnormal processing and presentation of self antigens. Superantigens are considered to be one of the most effective bacterial components to induce inflammatory reactions and to take part in the development and course of autoimmune mechanisms. It has long been known that defects in the host defense mechanism render the individual susceptible to infections caused by certain microorganisms. Impaired exclusion of microbial antigens can lead to chronic immunological activation which can affect the tolerance to self components. Defects in certain components of the immune system are associated with a higher risk of a development of autoimmune disease. The use of animal models for the studies of human diseases with immunological pathogenesis has provided new insights into the influence of immunoregulatory factors and the lymphocyte subsets involved in the development of disease. One of the most striking conclusion arising from work with genetically engineered immunodeficient mouse models is the existence of a high level of redundancy of the components of the immune system. However, when genes encoding molecules involved in T cell immunoregulatory functions are deleted, spontaneous chronic inflammation of the gut mucosa (similar to human inflammatory bowel disease) develops. Surprisingly, when such immunocompromised animals were placed into germfree environment, intestinal inflammation did not develop. Impairment of the mucosal immune response to the normal bacterial flora has been proposed to play a crucial role in the pathogenesis of chronic intestinal inflammation. The use of immunodeficient models colonized with defined microflora for the analysis of immune reactivity will shed light on the mode of action of different immunologically important molecules responsible for the delicate balance between luminal commensals, nonspecific and specific components of the mucosal immune system.     

Comparison of bond strengths of three denture base resins to treated nickel-chromium-beryllium alloy

The success of radiotherapy in eradicating tumours depends on the total radiation dose, but what limits this dose is the tolerance of the normal tissues within the treatment volume. Studies involving fibroblast survival have demonstrated the theoretical feasibility of a predictive assay of radiation sensitivity, but such an assay is still far from clinical application. Using pulsed-field gel electrophoresis (PFGE), we have quantified the initial "apparent" number of DNA double-strand breaks (dsb) induced by the radiation as an alternative measure of sensitivity in 2 different normal cell types from the same patients, epidermal skin cells and lymphocytes. We found significant inter-individual variation in the measured dsb (1-5 dsb/Gy/DNA unit). We also found a linear correlation between molecular damage in lymphocytes and skin samples from the same patient (slope = 0.83; r = 0.694; p = 0.0001). These results suggest that the initial number of dsb could be used as an indicator of the in vivo response to radiation.     

NIDA technical review: nitrite inhalants

Nitrite inhalants are commonly abused substances in the US and Europe. "Nitrite inhalants and AIDS" was a popular topic in the early 1980s when the cause of AIDS was not known. With the discovery of HIV, concern about nitrite use wained. However, nitrite inhalant use is associated with behavioral relapse and HIV transmission among gay men, with decreased lymphocyte counts and natural killer cell activity in laboratory studies, and remains a candidate "cofactor" in the pathogenesis of AIDS-related Karposi sarcoma. Discouraging nitrite use continues to be a worthwhile public health goal. Participants recommend specific research efforts.     

Muscle proton T2 relaxation times and work during repetitive maximal voluntary exercise

We studied the effects of progressive maximal voluntary handgrip contractions (MVCs) on muscle proton spin-spin (T2) relaxation times and work, measured as the integrated force vs. time curve (FTI). Six healthy volunteers performed 10, 20, 40, and 80 MVCs in a 0.35-T magnet on four separate occasions. Repeated measures analyses of variance of increases in T2 and FTI during successive bouts were significant (P < 0.005 and P < 0.001, respectively). FTI increased with successive bouts to a greater extent than did muscle T2 (P < 0.05). For T2, the Helmert contrast judged the 10-MVC response lower than the mean of the remaining responses (P < 0.005), and the differences between all others compared with the means of subsequent responses were not significant, indicating a "flattening" of the T2 response after the increase from 10 to 20 repetitions. For FTI, all the single degree of freedom Helmert contrasts were significant (P < 0.001), indicating a continual increase in response over increased MVCs. The curved nature of the T2 response conformed best to a hyperbolic function, suggesting that a limit of approximately 32% exists for the change in T2 during progressively longer bouts of MVCs. A limit in the T2 response is consistent with the existence of a limit in the amount of water that muscle can take up from the vasculature during exertion.     

Risk-benefit analysis for industrial and social needs

This study develops a decision method for evaluating the social acceptability of industrial controls on hazardous materials. Decisions are based on a "multiple criteria approach" that jointly considers measures such as risk-benefit tradeoff, minimum reducible health risk, maximum acceptable cost and implicit value of human life. Health risks are calculated by combining separate estimates of production and usage patterns, emissions to air and water, effectiveness of controls, pollutant dispersion and human susceptibility. Economic benefits consider employment, trade and consumer impacts, as well as direct costs of controls. The analysis focuses on asbestos as an example hazard. Relative values of hazard reduction alternatives are examined for asbestos manufacturing exhaust filters and for asbestos substitutes in brake linings. Preliminary calculations indicate risk reductions of these alternatives cannot justify their social costs.     

Blood and plasma selenium levels and GSH-Px activities in patients with arterial hypertension and chronic heart disease

Among the 57 monoclonal antibodies analyzed within the T-cell group of the Second International Swine CD Workshop, one mAb fell within cluster T14a that included the CD6 standard a38b2 (No. 175). The new mAb MIL8 (No. 082) and a38b2 both precipitated from activated T-cells a 150 kDa monomeric protein. Staining patterns on the various cell types were similar. There was no inhibition of binding of either mAb to peripheral blood T-cells with the opposite mAb. The new mAb, MIL8, reacts with a separate epitope on porcine wCD6.     

Event-related brain potentials during semantic categorization in normal aging and senile dementia of the Alzheimer's type

To assess the effects of normal aging and senile dementia of the Alzheimer's type (SDAT) on semantic analysis of words, we examined the N400 component of the event-related potential (ERP) elicited during the processing of highly constrained (opposites) and less constrained materials (category-category exemplars) in 12 young control subjects, 12 elderly control subjects and 12 patients with SDAT. We employed a priming paradigm in which a context phrase was spoken and a target word (congruent or incongruent) was presented visually. The N400 effect was reduced in amplitude and delayed in the elderly control group relative to that of the younger subjects, and was further attenuated in amplitude, delayed in latency and somewhat flatter in its distribution across the scalp in the SDAT patients. These findings are consistent with less efficient processing and integration of lexical items with semantic context in normal aging, which is further exacerbated by SDAT. Differences in the N400 range associated with the opposite and category conditions were observed only in the young subjects, suggesting less use of controlled attentional resources or perhaps weaker associative links with age.     

Activation of T lymphocytes by syngeneic murine intestinal smooth muscle cells

BACKGROUND & AIMS: Intestinal smooth muscle cells (ISMCs) express major histocompatibility complex II (MCH II) and intercellular adhesion molecule 1 (ICAM-1) after exposure to interferon gamma (IFN-gamma). T lymphocytes invade the intestinal musculature during Crohn's disease or pseudoobstruction. The aim of this study was to determine whether ISMCs activate syngeneic T cells via MHC II and ICAM-1. METHODS: Cultured murine ISMCs were exposed to IFN-gamma for 72 hours and analyzed for Mac-1 (CD11B CD18) antigen, MHC II, and ICAM-1 expression using enzyme-linked immunosorbent assay and fluorescence-activated cell sorter scan. T lymphocytes from mesenteric lymph nodes of ovalbumin-sensitized mice were examined for their ability to proliferate after coculture with IFN-gamma-pretreated and ovalbumin-pretreated ISMCs using [3H]thymidine incorporation. RESULTS: ISMCs expressed smooth muscle alpha-actin before and after IFN-gamma exposure. No macrophages were identified in these cultures. Exposure to IFN-gamma and ovalbumin for 72 hours induced MHC II and ICAM-1 expression; these treated ISMCs induced T-cell proliferation, whereas untreated ISMCs did not. T-cell proliferation was markedly enhanced by adding interleukin 2 and was blocked by antibodies against MHC II and ICAM-1. CONCLUSIONS: ISMCs activate T lymphocytes in an MHC II-linked manner and thus possess the ability to modulate immune function in the gut.