The organophosphate paraoxon has no demonstrable effect on the murine immune system following subchronic low dose exposure.

Paraoxon is the bioactive metabolite of the organophosphate pesticide parathion. Desulphuration of parathion by liver enzymes or sunlight results in the formation of paraoxon which inhibits acetylcholine esterase (AChE) activity. In the present study, we analyzed the effect of a 6-week, subchronic treatment with two different daily intraperitoneal doses (30 or 40 nmol) of paraoxon on the immune system of BALB/c mice. At a dose of 30 nmol/day, body weight of treated animals was unchanged compared to the controls. In contrast, the higher dose (40 nmol/day) induced a reduction in body growth, particularly in the first 3 weeks of treatment, peaking at week 2 when the saline group showed a 14.2-fold increase in body weight gain compared to paraoxon-treated animals. Moreover, mice treated with either dose of paraoxon had a >50% reduction in AChE activity during the first 3 weeks of treatment, but by the end of the treatment (week 6), AChE activity returned to normal. With regard to immunological parameters, there was no significant difference in either total spleen weight or in the ratios of various spleen cell populations between control and paraoxon-treated animals. Furthermore, no changes were observed in mitogen-induced cytokine secretion from splenocytes of paraoxon-treated mice. Finally, subchronic exposure to paraoxon did not alter mortality of mice exposed to a bacterial infection with Salmonella typhimurium. These data suggest that although subchronic exposure to paraoxon induced a transient inhibition in AChE activity, it had no demonstrable effect on the host immune system.

Iosimenol, a new non-ionic dimeric contrast medium, does not induce immunoreactivity in the popliteal lymph node assay.

Animal studies in mice were conducted to determine the potential immunoreactivity of the new non-ionic dimeric contrast medium (CM) iosimenol using the PLNA and flow cytometric analyses. Comparative studies were performed with iodixanol. The known immune-reactive substance strepozotocin (STZ) and vehicle injections served as positive and negative controls, respectively. Our experiments did not show any immunological effect of iosimenol, concluding that the new CM iosimenol may be beneficial for use in high-risk patients.

The Src-protein tyrosine kinase Lck is required for IL-1-mediated costimulatory signaling in Th2 cells.

Src-protein tyrosine kinases are intimately involved in TCR-initiated signaling in T lymphocytes. One member of this family, Lck, is also involved in CD28-mediated costimulation in Th1 cells. In Th2 lymphocytes, the costimulatory signal can also be provided by the interaction of IL-1 with type I IL-1R (IL-1RI), culminating in the activation of NF-kappaB transcription factors. Proximal steps in the IL-1R pathway, however, remain poorly understood, and there is conflicting evidence as to the importance of tyrosine phosphorylation in IL-1R signaling. We have addressed this issue by examining the ability of IL-1 to costimulate the activation of Lck-deficient Th2 cells. Our data demonstrate that, in the absence of Lck, the IL-1 costimulatory pathway is blocked despite the expression of normal levels of IL-1RI. Moreover, the block is associated with a defective degradation of IkappaB-alpha and an incomplete activation of NF-kappaB heterodimeric complexes. Protein expression of NF-kappaB monomers, including p50, p65, and c-Rel, is equivalent in both wild-type and Lck-deficient Th2 cell clones. Finally, we demonstrate that, in normal Th2 cells, stimulation with IL-1 leads to a rapid induction in tyrosine phosphorylation of several substrates including Lck itself. These findings strongly suggest that Lck is required for signaling in the IL-1 costimulatory pathway in Th2 lymphocytes.

Influence of vector-encoded cytokines on anti-Salmonella immunity: divergent effects of interleukin-2 and tumor necrosis factor alpha.

Attenuated Salmonella strains are of interest as new vaccine candidates and as vectors of cloned genes of other organisms. Attenuated strains expressing specific cytokines were constructed as a means of manipulating the immune response in various disease settings. In the present study, interleukin-2 (IL-2)-expressing (GIDIL2) or tumor necrosis factor alpha (TNF-alpha)-expressing (GIDTNF) strains were compared with the parent strain (BRD509) for the effect of cytokines on anti-Salmonella immunity. Expression of IL-2 resulted in a rapid clearance of the organism soon after vaccination. The reduction in GIDIL2 CFU was 50- to 300-fold higher than that of BRD509 and correlated with a markedly decreased splenomegaly. Furthermore, no evidence for any significant activation, including upregulation of surface markers and production of nitric oxide (NO), was observed in spleens of GIDIL2-injected mice. In contrast, the host response to GIDTNF was marked by an early, strong, splenic cellular influx, but surprisingly, the degree of induced splenomegaly and NO secretion was only 50% of that observed in BRD509-treated mice. Despite this, bacterial colonization of the spleen in GIDTNF-immunized animals was either slightly decreased from or equivalent to that of the BRD509-treated group, suggesting the induction of additional antimicrobial mechanisms by TNF-alpha. In vivo protection studies demonstrated that, at limiting doses, GIDIL2 was inferior to GIDTNF and BRD509 in its capacity to protect against virulent challenge. At high doses, however, all three strains exhibited equal protective efficacy. These results demonstrate that the immune response against intracellular bacteria can be manipulated by pathogen-expressed cytokines and open the way for further fine tuning of immune responses not only to Salmonella strains themselves but also to the heterologous gene(s) carried by them.

Cell-specific expression of the human Na+,K(+)-ATPase beta 2 subunit isoform in the nonpigmented ciliary epithelium.

PURPOSE: To evaluate the patterns of expression of beta subunit isoforms of the Na+,K(+)-ATPase and H+,K(+)-ATPase in the human eye and to determine the cell-specific distribution of the beta 2 subunit in the human ciliary epithelium. METHODS: Total RNA extracted from human ocular tissues was screened by Northern blot analysis with cDNA probes for the human Na+,K(+)-ATPase subunit isoforms (beta 1 and beta 2) or the H+,K(+)-ATPase (alpha and beta) subunits. Antibodies were raised to the amino and carboxyl terminal regions of the human beta 2 isoform. Polymerase chain reaction was used to verify the expression of beta 2 subunit in nonpigmented ciliary epithelial cells (NPE). RESULTS: Transcripts for the Na+,K(+)-ATPase beta 1 and beta 2 subunit isoforms were present at different levels in all the ocular tissues except the lens, which expressed only beta 1. No transcripts for the alpha or beta subunits of the H+,K(+)-ATPase were detected in the eye. Isoform beta 2 specific anti-peptide antibodies V15E (N-terminus) and A18R (C-terminus) recognized a 55- to 60-kDa protein in the ciliary epithelium and the core protein of 32 kDa after N-glycanase treatment. Immunocytochemical localization within the ciliary epithelium indicates that the Na+,K(+)-ATPase beta 2 isoform is expressed preferentially in the NPE cells. The expression of Na+,K(+)-ATPase beta 2 isoform in the human NPE cell line, ODM-2, was confirmed by polymerase chain reaction amplification and Southern blot analysis. CONCLUSIONS: The Na+,K(+)-ATPase beta 2 subunit isoform, but not H+,K(+)-ATPase, was expressed widely in ocular tissues of the human eye. The restricted cellular distribution of beta 2 isoform within the NPE cells represents an important differential gene marker associated with the multiple alpha subunit isoforms of Na+,K(+)-ATPase.