Ii Expression Research Articles

Tumor Necrosis Factor α Regulates Expression of the Major Histocompatibility Complex Class II-Associated Invariant Chain by Binding of an NF-κB-Like Factor to a Promoter Element

Expression of the major histocompatibility complex (MHC) class I and class II antigens and the class II-associated invariant chain (Ii) is strongly increased by treatment of cells with tumor necrosis factor alpha (TNF-alpha) and gamma interferon. We investigated elevation of expression of the invariant chain gene by TNF-alpha. Rat fibroblast cells transfected with the mouse Ii gene containing 802 base pairs of 5' sequences could be stimulated for Ii expression by treatment with TNF-alpha. Analysis of 5'-deleted Ii gene promoter-CAT constructs provided evidence for the presence of a TNF-alpha response box (TRB). Cloning of TRB in front of a non-TNF-alpha-responsive promoter could transfer the TNF-alpha stimulatory effect. We demonstrate binding of a TNF-alpha-induced factor to a kappa B-like motif within TRB. Mutations introduced into the kappa B element of the Ii promoter-CAT plasmid abolished the TNF-alpha-mediated stimulatory effect. Comparison of the TNF-alpha-induced factor and lipopolysaccharide-induced NF-kappa B in gel mobility shift assays upon partial protease digestion suggests similar DNA-binding protein cores. Further support for the NF-kappa B-like nature of the TNF-alpha-induced factor was obtained in methylation interference assays. The TNF-alpha-induced nuclear factor comprises DNA contact sites that are identical to those described for NF-kappa B. This TNF-alpha-induced factor also interacts with kappa B-like sequences of the MHC Kb, Ek alpha, and beta 2-microglobulin promoter, suggesting a common TNF-alpha-mediated regulatory signal for expression of MHC antigens and Ii.

Cooperative effect of interferon‐γ and tumor necrosis factor‐α on the induction of the class II antigen‐associated invariant chain expression

The regulation of the invariant chain (Ii) expression was studied in the human colon carcinoma cell line HT-29 that constitutively expressed neither Ii nor class II antigens. Upon stimulation of HT-29 cells with a combination of human recombinant tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), expression of mRNA and protein of the invariant chain were induced. In contrast, administration of TNF-alpha or IFN-gamma alone had no effect. A delayed induction of Ii mRNA, which was first detected 10-12 h after stimulation, was observed; this suggests an indirect regulatory mechanism. Stimulation with both IFN-gamma and TNF-alpha led to the co-expression of class II antigens with the invariant chain. In order to study the genetic basis for this stimulation the murine invariant chain gene (800 bp 5' flanking sequences and the structural gene) was transfected into HT-29 cells and transfected cells were tested for the ability to respond to IFN-gamma and TNF-alpha. Simultaneous application of both cytokines had a strong effect on the induction of the murine invariant chain. IFN-gamma alone had no effect and TNF-alpha only marginally stimulates murine invariant chain expression. The transfection experiment indicates that the murine invariant chain gene construct contains the structural elements which are responsible for regulation with IFN-gamma and TNF-alpha. We determined whether the cooperative effect of TNF-alpha and IFN-gamma is also found in vivo. Stimulations of mice were performed with TNF-alpha, IFN-gamma and a combination of both. The immunohistological analysis of kidney tissue sections revealed that TNF-alpha had no effect on Ii and Ia expression. Upon IFN-gamma treatment a minor subset of renal tubules showed staining for Ii, and less prominently also for Ia. However, simultaneous application of both cytokines led a strong induction of both Ii and Ia antigens in renal epithelial cells, thus suggesting that this synergistic effect potentially occurs under physiological conditions.

Differential expression of HLA-DR, HLA-DP, HLA-DQ and associated invariant chain (Ii) in normal colorectal mucosa, adenoma and carcinoma.

The expression of MHC class II antigens (HLA-DR, HLA-DP and HLA-DQ) and the associated invariant chain (Ii) was studied in epithelial cells of normal colorectal mucosae, colorectal adenomas and carcinomas, using a sensitive immunoperoxidase technique with monoclonal antibodies on frozen sections. In contrast to class II antigens, Ii was detected in some normal mucosae distant from the tumour. In residual non-neoplastic mucosa adjacent to carcinomas, Ii and class II antigens were induced in the order Ii greater than or equal to HLA-DR greater than or equal to HLA-DP greater than or equal to HLA-DQ, the reactions being most pronounced in cases with inflammatory alteration of the crypts. In 22/37 adenomas and 77/123 carcinomas, Ii expression clearly exceeded class II antigen expression. Class II antigens were found in 20/37 adenomas and 62/123 carcinomas, mostly in a non-coordinate manner, following the above order. A detailed analysis of the expression patterns in normal and neoplastic colon epithelial cells revealed a closer association of HLA-DP with HLA-DQ than of HLA-DR with HLA-DP, or HLA-DQ.

Differential expression of Ia and Ia-associated invariant chain in mouse tissues after in vivo treatment with IFN-gamma.

B10.BR mice were injected i.v. with varying doses of recombinant IFN-gamma on three consecutive days. In tissue sections of 13 organs, the distribution of Ia antigens and Ia-associated invariant chain (Ii) was studied by using an immunoperoxidase technique. In the control animal, Ia and Ii were shown to be co-expressed in most tissues. However, on Kupffer cells, a small number of hepatocytes, and a subset of lymphocytes in lymph nodes and in the splenic red pulp only Ii, and no Ia, was detectable. In contrast, strongly Ia+ interdigitating reticulum cells of T-dependent areas of lymph nodes and spleen were only weakly stained for Ii. IFN-gamma treatment resulted in a dramatic increase of MHC antigen expression throughout the body, with striking differences in the inducibility of certain tissues for Ia and Ii: Bronchial epithelium was clearly induced to express the invariant chain, whereas Ia antigens remained entirely absent. Moreover, in kidney tubules and colon epithelium, Ii was induced more broadly than Ia. In contrast to the induction of Ii on endothelial cells of larger vessels in kidney, heart, and lungs, no de novo expression of Ia or Ii in capillary endothelial cells was observed. The number of detectable Ia+/Ii+ interstitial dendritic cells considerably increased upon exposure to IFN-gamma. Neither neurons nor glial cells were induced to MHC antigen expression. Our data demonstrate that IFN-gamma applied i.v. is a potent inducer or enhancer of Ia antigens and invariant chain in a variety of cell types.

Differential effect of TPA and n‐butyrate on induction of Ii and EBV antigens in the P3HR‐1 lymphoblastoid cell line

The aim of this study was to test whether EBV induction by TPA or n-butyrate was related directly to hyperexpression of Ii, an electrophoretically invariant, 35 000 dalton, HLA-DR antigen-associated glycoprotein which is abundantly detected in EBV freshly transformed cells and is enhanced by EBV superinfection of lymphoblastoid cell lines. P3HR-1 lymphoblasts were treated with n-butyrate or TPA in variable doses and durations. The augmented expression of Ii, EBV antigens (EA and VCA), DNA synthesis, and cell growth and viability were monitored. n-Butyrate induced hyperexpression of Ii at 2 days with a maximal effective dose of 4 mM, induced EBV antigens (EA and VCA) in 36 per cent of the cells at 2 days, inhibited DNA synthesis and cell growth, and was not cytolytic at 48 h when Ii induction was maximal. TPA did not induce hyperexpression of Ii, induced EBV antigens (EA) in 30 per cent of the cells at 4 days, did not inhibit DNA synthesis and cell growth, and was not cytolytic in the time course and doses studied. Ii expression, therefore, did not appear to be an obligatory consequence of EBV antigen induction. Ii induction might be related to an effect of EBV inducers on cellular DNA synthesis, or on control of the cell cycle, or directly upon Ii gene regulation.

Enhanced Ii expression after n-butyrate treatment of a P3HR-1 Burkitt's lymphoma subline which does not express HLA-D.

Treatment of P3HR-1 Burkitt's lymphoma cultured cells with 4 mM n-butyrate for 48 h induced the abundant expression of a 35 000 dalton, microsomal membrane protein which was demonstrated to be the electrophoretically invariant Ii molecule. To prove this point, [35S]methionine-labelled, microsomal membrane proteins or immunoprecipitates of such detergent-solubilized proteins were subjected to electrophoresis either in SDS gels or in two-dimensional, nonequilibrium pH gradient gels. The induced p35 molecule was judged to be Ii by molecular weight and isoelectric characteristics and by immune complex associations. The abundant expression of Ii on butyrate-treated P3HR-1 cells mimicked the high level of expression of p35 or Ii on leukemic cells of a subset of patients with hairy cell leukemia. Alpha and beta chains of the HLA-D complex were absent from the P3HR-1 cell line and present in the Jijoye parent from which mutant P3HR-1 was derived. This relatively simple model can lead to the study of inducible synthesis, processing and expression of Ii, with or without HLA-D alpha and beta chains.