Construction of internal cDNA competitors for measuring IL-10 and IL-12 cytokine gene expression in swine

A competitive PCR assay (cPCR) was used to quantify swine cytokine responses to parasite infection. Internal standards (deleted cDNA competitor molecules [DcDNA mimics]) were produced and tested for swine interleukin-12 (IL-12), interleukin-10 (IL-10) and hypoxanthine phosphoribosyltransferase (HPRT) from PCR generated cDNA cloned in plasmid vectors. Deletion clones for the cDNA competitor molecules (DcDNA mimics) were generated for IL-10, IL-12 and HPRT by PCR in a single step and verified by (1) amplification of the expected smaller PCR product with the original primers, (2) appropriate fragment size released by restriction digestion of the deleted clone, and (3) correct sequence of the new DcDNA insert. DcDNA mimics were used to quantitate cytokine gene mRNA production during experimental and natural infections of swine with the gastrointestinal nematode parasite Trichuris suis. Mesenteric lymph node cells were collected from control and infected pigs at the time of maximal pathogenicity (35 days after infection) and snap frozen. After RNA extraction, samples were reverse transcribed (RT) to cDNA. cPCR was performed using the housekeeping gene HPRT DcDNA mimic and HPRT specific primers to insure RNA integrity and concentration. Cytokine cDNA content in these samples was then quantitated using cytokine mimics and gene specific primers. IL-10 gene expression in MLN draining the colon of pigs experimentally infected with T. suis increased 10-20 fold at day 35 compared to control pigs. IL-12 gene expression was not detectable in MLN of these pigs, but was detectable in MLN of pigs exposed naturally to T. suis on a contaminated dirt lot that also exhibited signs of secondary bacterial invasion. Swine IL-10 and IL-12 gene expression can be quantitated in local mesenteric tissues. This cPCR assay will enable scientists to quantitate cytokine gene expression in swine and determine the nature of immune responses to important infectious diseases.

Direct thymic involvement in anterior chamber-associated immune deviation: evidence for a nondeletional mechanism of centrally induced tolerance to extrathymic antigens in adult mice

Recent reports have suggested that the dichotomy between central (thymic) and peripheral T cell tolerance is not absolute and that self-tolerance in perinatal animals may also involve the intrathymic generation and release to the periphery of Ag-specific immunoregulatory T cells. We have expanded this concept to include tolerance to non self Ags administered extrathymically to adult animals. In this study, we use the anterior chamber-associated immune deviation (ACAID) to demonstrate that central regulation of acquired peripheral tolerance can be induced in adult mice by the intraocular administration of low doses of nonself Ag. The results show that adult thymectomy prevents the inhibition of trinitrophenol (TNP)-specific delayed-type hypersensitivity, which normally occurs after injection of TNP-BSA into the anterior chamber (AC) of the eye. Thymocytes obtained from mice 1 to 3 days, but not 5 to 7 days, after AC injection of TNP-BSA or BSA alone specifically transfer inhibition of delayed-type hypersensitivity to mice primed with the homologous Ag. The latter observation, when correlated with the time of onset of ACAID, suggests that immunoregulatory T cells are formed in the thymus within 24 h and are exported to the peripheral lymphoid tissues between 2 and 5 days after AC injection of Ag. Immunomagnetic separation of thymocytes revealed that the immunoregulatory activity resides within the minor subset of CD4-, CD8-, TCR-alphabeta+ cells, previously postulated to induce fas ligand-mediated apoptosis and Th1 to Th2 immune deviation. Hence, the present study identifies ACAID as a prototypical model of centrally induced, nondeletional tolerance to extrathymic nonself Ags.

Direct thymic involvement in anterior chamber-associated immune deviation: evidence for a nondeletional mechanism of centrally induced tolerance to extrathymic antigens in adult mice

Recent reports have suggested that the dichotomy between central (thymic) and peripheral T cell tolerance is not absolute and that self-tolerance in perinatal animals may also involve the intrathymic generation and release to the periphery of Ag-specific immunoregulatory T cells. We have expanded this concept to include tolerance to non self Ags administered extrathymically to adult animals. In this study, we use the anterior chamber-associated immune deviation (ACAID) to demonstrate that central regulation of acquired peripheral tolerance can be induced in adult mice by the intraocular administration of low doses of nonself Ag. The results show that adult thymectomy prevents the inhibition of trinitrophenol (TNP)-specific delayed-type hypersensitivity, which normally occurs after injection of TNP-BSA into the anterior chamber (AC) of the eye. Thymocytes obtained from mice 1 to 3 days, but not 5 to 7 days, after AC injection of TNP-BSA or BSA alone specifically transfer inhibition of delayed-type hypersensitivity to mice primed with the homologous Ag. The latter observation, when correlated with the time of onset of ACAID, suggests that immunoregulatory T cells are formed in the thymus within 24 h and are exported to the peripheral lymphoid tissues between 2 and 5 days after AC injection of Ag. Immunomagnetic separation of thymocytes revealed that the immunoregulatory activity resides within the minor subset of CD4-, CD8-, TCR-alphabeta+ cells, previously postulated to induce fas ligand-mediated apoptosis and Th1 to Th2 immune deviation. Hence, the present study identifies ACAID as a prototypical model of centrally induced, nondeletional tolerance to extrathymic nonself Ags.

A national survey of physicians' and nurses' attitudes toward endoscope cleaning and the potential for cross-infection

To elicit information on endoscope cleaning practices and the perceived risk of cross-infection, questionnaires were mailed to 500 physicians and 1,000 gastroenterology nurses and associates in November and December 1991. The survey results indicated that while the majority (83% of nurse/associates and 82% of physicians) expressed satisfaction with current cleaning methods, levels of confidence in endoscope reprocessing varied in several key areas. Concern about the potential for device-borne human immunodeficiency virus transmission was expressed by 82% of nurses and 87% of physicians, while 75% of nurses and 53% of physicians feared being liable should cross-infection occur. While most respondents (86% of physicians and 30% of nurses) were unaware of cross-infection incidents, 6% of nurses reported outbreaks in their institutions. According to survey responses, the risk of cross-infection may be attributable to variable cleaning practices--failure to clean scopes before placing them in disinfectant, abbreviated overall cleaning times, and inconsistent disinfectant immersion times--that may be compounded by unreliable automatic disinfectors. At least once a year endoscopes were blocked by debris according to 74% of nurses and 72% of physicians. Reactions to glutaraldehyde had been experienced by 87% of nurses and 65% of physicians. Gastroenterology professionals may be unaware of the actual incidence of cross-infection, but recognize its potential. Lapses in cleaning practices and the difficulty in monitoring postendoscopy nosocomial infections add to their uncertainty.

Astrocytes synthesize apolipoprotein E and metabolize apolipoprotein E-containing lipoproteins

We have previously demonstrated that astrocytes synthesize and secrete apolipoprotein E in situ. In the present work, primary cultures of rat brain astrocytes were used to study apolipoprotein E synthesis, secretion, and metabolism in vitro. The astrocytes in culture contained immunoreactive apolipoprotein E in the area of the Golgi apparatus. Incubation of the astrocytes with [35S]methionine resulted in the secretion of labeled immunoprecipitable apolipoprotein E, which constituted 1-3% of the total secreted proteins. The apolipoprotein E secreted in culture and the apolipoprotein E in rat brain extracts differed from serum apolipoprotein E in two respects: both had a slightly higher apparent molecular weight (approx. 36,000) and more acidic isoforms than serum apolipoprotein E. Sialylation of the newly secreted apolipoprotein accounted for the difference in both the apparent molecular weight and isoelectric focusing pattern of newly secreted apolipoprotein E and plasma apolipoprotein E. The astrocytes possessed apolipoprotein B,E(LDL) receptors capable of binding and internalizing apolipoprotein E-containing lipoproteins. The uptake of lipoproteins by the cells led to a reduction in the number of cell surface receptors and to the intracellular accumulation of cholesteryl esters. Since apolipoprotein E is present within the brain, and since brain cells can express apolipoprotein B,E(LDL) receptors, apolipoprotein E-containing lipoproteins may function to redistribute lipid and regulate cholesterol homeostasis within the brain.