The transcription factor NF-B plays an important role in the regulated expression of cytokines in human monocytes. A p100 subunit of NF-B has IB-like properties by sequestering the p65 transactivating subunit in the cytosol of cells. In transient transfection assays we demonstrated that p100 has an inhibitory effect on the NF-B-dependent IL-6 promoter activity. In view of this finding, we studied the regulation of the p100 subunit in human monocytes in response to LPS, the inflammatory cytokines IL-1␤ and TNF-␣ and lymphokines. The results demonstrate that LPS, IL-1␤, and TNF-␣ induce p100 expression at mRNA and protein level while IFN-␥, IL-3 and IL-4/IL-10 have no effect. The induction of p100 expression was shown to be mediated by a two-fold increase in the p100 transcription rate and a two-fold increase in p100 mRNA stability. Furthermore the p100 mediated upregulation was dependent on a tyrosine kinase dependent pathway rather than the protein kinase C pathway. NF-B is a complex of either p50 homodimers or a p50/p65 heterodimer. The latter is known to strongly autoregulate p100 transcription. We therefore examined the composition of NF-B induced by LPS vs the different lymphokines. LPSinduced NF-B showed a distinct p65 supershift whereas the composition of NF-B induced by different lymphokines did not show a change in p65. We conclude that the p100 subunit of the transcription factor NF-B is induced by different inflammatory mediators while lymphokines fail to induce p100 expression which may be caused by the induction of NF-B predominantly consisting of p50 homodimers.

Human T cells were studied with regard to the regulation of interleukin- 4 (IL-4) and IL-3 gene expression. IL-4 and IL-3 mRNA were undetectable in unstimulated T cells. On activation with the lectin concanavalin A (Con A), both IL-4 and IL-3 mRNA were expressed. Accumulation of IL-4 mRNA peaked after 6 to 12 hours, whereas IL-3 mRNA levels peaked after 3 to 6 hours of stimulation with Con A. Nuclear run-on assays showed a low constitutive transcription for both genes. The transcription rates were increased by Con A resulting in a peak for IL-4 after 1 hour (30% increase) and for IL-3 after 3 hours (40% increase) of Con A treatment. mRNA stability studies demonstrated that on activation with Con A both messages decayed with a half-life of approximately 90 minutes. No IL-4 or IL-3 mRNA expression was induced by the protein kinase C activator phorbol myristate acetate (PMA). However, PMA augmented the Con A- induced IL-4 and IL-3 mRNA accumulation. This was shown to be mediated at posttranscriptional level by a large increase in the stability of both messages (t 1/2 > 3 hours). The transcription rate of both genes was also enhanced by Con A+PMA and reached peak levels for IL-4 after 1 hour (90% increase) and for IL-3 after 3 hours (70% increase) of stimulation. Furthermore, it appeared that the induction of IL-4 mRNA was dependent on protein synthesis because cycloheximide (CHX) blocked the Con A- and Con A+PMA-induced expression of IL-4 mRNA. In contrast, CHX inhibited, but failed to completely block, the Con A- and Con A+PMA- induced IL-3 mRNA expression, whereas the expression of both genes was completely blocked by cyclosporine A. With regard to the secretion of IL-4 protein it was shown that it closely follows the accumulation of IL-4 mRNA. Taken together, the data show that expression of the IL-4 and IL-3 genes in human T cells is controlled by different activation pathways that affect the gene regulation at transcriptional and posttranscriptional levels.

Human recombinant interleukin-4 (IL-4) was studied for its effects on the expression of granulocyte-colony stimulating factor (G-CSF) mRNA in human adherent monocytes in the absence and presence of endotoxin and interleukin 1 (IL-1). IL-4 (15 ng/ml) did not induce G-CSF transcripts in monocytes but suppressed the endotoxin-induced G-CSF expression when added simultaneously. Sequential treatment of monocytes with IL-4 followed by endotoxin suppressed G-CSF mRNA induction totally. This effect was independent of the presence of fetal bovine serum but dependent of the IL-4 dose. Comparable results were obtained with IL-1. IL-1 (50 U/ml) induced G-CSF expression in human adherent monocytes which could be counteracted by IL-4 pretreatment. In addition, it was shown that the induction of G-CSF mRNA by the calcium-ionophore A23187 or by c-AMP elevating agents could be blocked by IL-4. These suppressive effects of IL-4 were not related to changes in the half-life of G-CSF mRNA and were independent of protein synthesis. Finally it was demonstrated that IL-4 had comparable effects on the G-CSF secretion of endotoxin and IL-1 stimulated human monocytes by using a murine bone marrow assay. These results indicate that IL-4 down-regulates the expression of G-CSF gene and secretion of proteins in human activated monocytes.

Interleukin-4 (IL-4) modulates the survival, proliferation, and differentiation of a variety of hematopoietic cells. The effects are mediated through a single class of high-affinity receptors for IL-4. To understand the biologic effects of IL-4 on human T cells, we studied the regulation of IL-4 receptor (IL-4R) gene expression. We showed that IL-4R mRNA accumulation in human T cells is enhanced fourfold after activation of different secondary signaling pathways by concanavalin A (Con A), phorbol myristate acetate (PMA), the calcium ionophore A23187, and combinations of these factors. This could be ascribed to an increase in the IL-4R transcription rate and to stabilization of IL-4R mRNA resulting in a half-life of 80 to 90 minutes (v 35 to 40 minutes in resting T cells). IL-4 did enhance the IL-4R mRNA accumulation by a factor 10, which was caused by an increase in the IL-4R transcription rate and prolonging the half-life of IL-4R transcripts to 140 to 160 minutes. Finally, it was shown that A23187 induced IL-4R mRNA expression is a protein synthesis-dependent process. In contrast, Con A- , PMA-, Con A + PMA-, and Con A + A23187-induced expression of IL-4R mRNA is protein-synthesis independent. Cyclosporine A inhibited the A23187- and Con A + A23187-induced IL-4R mRNA accumulation, whereas Con A-, PMA-, and Con A + PMA-induced IL-4R mRNA expression was not affected by this drug. These data indicate that expression of IL-4 receptors on human T cells can be modulated by different intracellular signaling pathways at both transcriptional and posttranscriptional levels.

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We studied the effect of interleukin-4 (IL–4) on the lipopolysaccharide (LPS) induction of two immediate early genes c-fos and c-jun. These genes encode proteins that form the dimeric complex activator protein-1 (AP-1), which is active as a transcriptional factor. Maximal accumulation of either c-fos and c-jun messenger RNA (mRNA) occurred 30 minutes after LPS addition. When cells were treated with IL–4 for 5 hours before LPS activation, both the c-fos and the c-jun mRNA expression was decreased. The inhibition of c-fos and c-jun expression by IL-4 in LPS-treated cells was shown to be due to a lower transcription rate of the c-fos and c-jun genes. IL–4 did not affect the stability of the c-fos and c-jun transcripts. Finally, using electrophoretic mobility shift assays, evidence was obtained that IL-4 inhibits LPS-induced expression of AP-1 protein. These data indicate that IL-4 suppresses the induction of transcription factors in human activated monocytes.

The human pancarcinoma-associated epithelial glycoprotein-2 (EGP-2), also known as 17-1A or Ep-CAM, is a 38-kDa transmembrane antigen, commonly used for targeted immunotherapy of carcinomas. Although strongly expressed by most carcinomas, EGP-2 is also expressed in most simple epithelia. To evaluate treatment-associated effects and side-effects on tumor and normal tissue respectively, we generated an EGP-2-expressing transgenic Wistar rat. To express the cDNA of the EGP-2 in an epithelium-specific manner, the 5' and 3' distal flanking regions of the human keratin 18 (K18) gene were used. EGP-2 protein expression was observed in the liver and pancreas, whereas EGP-2 mRNA could also be detected in lung, intestine, stomach and kidney tissues. In this rat, EGP-2-positive tumors can be induced by injecting a rat-derived carcinoma cell line transfected with the GA733-2 cDNA encoding EGP-2. Transgenic rats were used to study specific in vivo localization of an i.v. anti-EGP-2 monoclonal antibody, MOC31, applied i.v. Immunohistochemical analyses showed the specific localization of MOC31 in s.c. induced EGP-2-positive tumors, as well as in the liver. In contrast, in EGP-2-transgenic rats, MOC31 did not bind to EGP-2-negative tumors, the pancreas, or other normal tissues in vivo. In conclusion, an EGP-2-transgenic rat model has been generated that serves as a model to evaluate the efficacy and safety of a variety of anti-EGP-2-based immunotherapeutic modalities.

N-Acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-L-alanyl-D-isoglutam yl-m- diaminopimelyl-D-alanine [G (Anh)MTetra], a naturally occurring breakdown product of peptidoglycan from bacterial cell walls, was studied for its ability to induce granulocyte colony-stimulating factor (G-CSF) mRNA and protein expression in human adherent monocytes. Resting monocytes did not express G-CSF mRNA or secrete G-CSF protein. In contrast, monocytes exposed to G(Anh)MTetra showed a dose-dependent increase in G-CSF mRNA accumulation, which correlates with the secretion of G-CSF protein. Maximal levels of G-CSF mRNA were reached within 2 h of activation. Expression of G-CSF was mediated by an increase in the stability of G-CSF transcripts rather than by an increase in the transcription rate of the G-CSF gene. Experiments with the protein synthesis inhibitor cycloheximide revealed that G(Anh)MTetra-induced G-CSF mRNA expression was independent of new protein synthesis. Furthermore, it was shown that the effect of G(Anh)MTetra was regulated by a protein kinase C-dependent pathway, whereas protein kinase A and tyrosine kinases were not involved. Finally, it was shown that G(Anh)MTetra also induced G-CSF mRNA expression in human endothelial cells. The data indicate that, besides lipopolysaccharide, other naturally occurring bacterial cell wall components are able to induce G-CSF expression in different hematopoietic cells.