IL-6R mRNA Research Articles

Spontaneous expression of the interleukin 2 receptor gene and presence of functional interleukin 2 receptors on T lymphocytes in the blood of individuals with active pulmonary sarcoidosis.

Current concepts of the pathogenesis of sarcoidosis suggest that the expanded numbers of activated T-helper/inducer cells at sites of disease activity result, at least in part, from their proliferation in the local milieu. Normal clonal proliferation of T cells involves activation and expression of the IL 2 receptor (IL 2R) gene. Thus, knowing that IL 2R mRNA transcripts are relatively long lived, we hypothesized that sarcoid blood T cells may contain IL 2R mRNA transcripts and express functional surface IL 2R, although the cells are probably activated elsewhere. Northern analysis using a 32P-labeled cDNA probe for the IL 2R p55 protein demonstrated that blood T cells of patients with active sarcoidosis, but not of normal patients, express 3.5- and 1.5-kb IL 2R mRNA transcripts, the same as those observed in normal T cells activated in vitro. Consistent with this, using flow cytometry and an MAb directed against the IL 2R p55 protein (2A3), we observed detectable levels of IL 2R surface protein on increased numbers of blood T cells of active sarcoidosis patients (4.7 +/- 0.9%) compared with blood T cells of normal patients (0.9 +/- 0.2%). Importantly, when the sarcoid blood T cells were exposed to IL 2 in vitro, they proliferated at a rate greater than that of normal blood T cells under the same conditions, suggesting that the IL 2R spontaneously expressed by sarcoid blood T cells were functionally active. In the context of the known compartmentalization of spontaneous IL 2 production and T cell proliferation at sites of disease in active pulmonary sarcoidosis, these IL 2R positive blood T cells would probably have a proliferative advantage if they trafficked to sites of active sarcoidosis, such as the lower respiratory tract.

P55 IL-2 receptor mRNA precursors in murine T lymphocyte nuclei.

An unusual family of cDNA clones homologous to human p55 IL-2R sequences was isolated from the murine HT-2 Th cell line. These clones were mapped, partially sequenced, and compared with previously published human and mouse IL-2R sequences. They appear to consist of various combinations of exons and introns, suggesting that they are derived from p55 IL-2R mRNA precursors. The configuration of exons in the splicing intermediates indicates that the murine and human gene organizations are similar and that the 3' end of intron 3 is well conserved between the two species. RNA mapping experiments using nuclear, cytoplasmic, and total RNA and probes derived from various parts of the p55 IL-2R gene support and extend the sequence data. They indicate that detectable amounts of immature p55 IL-2R mRNA are found specifically in the cell nucleus of the HT-2 cell line. Similar data were obtained for the Th cell clone 52.3 and the cytotoxic T cell line CTLL. All these results indicate that the T cell nucleus contains significant amounts of immature p55 IL-2R mRNA.

Induction and regulation of CD2 mRNA in human lymphocytes.

Herein we studied the accumulation and decay of CD2 mRNA in human PBMC stimulated with PHA. The data show that CD2-specific messages are present in low quantities in resting PBMC and are rapidly increased by five- to sevenfold within 24 h of addition of optimal amounts of PHA. Similar induction of CD2 mRNA was seen after stimulation of PBMC with anti-CD3 mAb and PMA. Peak levels of CD2 message were maintained until 72 h post-stimulation and declined gradually thereafter. Despite stimulation with Staphylococcus aureus and PMA, purified B cells failed to demonstrate any CD2 mRNA. Unlike transferrin or IL-2R mRNA, Il-2 had no effect on the accumulation of CD2 messages in resting or PHA-stimulated PBMC. The time course of CD2 mRNA accumulation preceded lymphocyte proliferation and the appearance of additional cell surface CD2 Ag. The decay of CD2 mRNA was very rapid, with a t 1/2 of approximately 45 min. The protein synthesis inhibitor, cycloheximide, increased its half-time by fourfold to 3.5 h. The data imply the existence of a labile factor, dependent on protein synthesis that is important in the regulation of CD2 mRNA. Compared to other PHA-inducible lymphocyte genes, the kinetics of CD2 transcript accumulation are most reminiscent of the oncogenes N-ras and c-abl.

Lymphocytes isolated from the intestinal lamina propria of normal nonhuman primates have increased expression of genes associated with T-cell activation

Synthesis of interleukin-2 (IL-2) and expression of interleukin-2 receptors play central roles in T-cell activation, proliferation, and differentiation. The state of activation of T lymphocytes in the intestinal lamina propria was compared with that of circulating lymphocytes and lymphocytes isolated from the spleen or mesenteric lymph nodes of normal nonhuman primates. Lamina propria lymphocytes (LPL) had significantly higher proliferation in response to recombinant IL-2 compared with the other populations. In agreement with this finding, LPL had a significantly higher percentage of interleukin-2 receptor-positive (IL-2R+) cells as determined by staining with fluoresceinated monoclonal anti-IL-2R antibody. Two-color immunofluorescence staining showed that both CD4+ and CD8+ lamina propria T cells were IL-2R+. It was also found that the percentage of major histocompatibility complex class II-positive T cells was higher in the lamina propria. Northern blot analysis with a cDNA specific for the IL-2R showed that unstimulated LPL had easily detectable IL-2R mRNA, whereas no IL-2R mRNA was found in unstimulated lymphocyte populations from other sites. The activation of the IL-2R gene in LPL was not associated with the activation of other cellular genes (actin, major histocompatibility complex class I). Although no IL-2 bioactivity was measured in culture supernatants of unstimulated lymphocytes, concanavalin A-stimulated LPL produced significantly more IL-2 than other lymphocytes. This finding was confirmed at the molecular level as IL-2 mRNA was not detected in unstimulated LPL but was found in concanavalin A-stimulated LPL. Thus, normal lamina propria T lymphocytes have selective expression of genes associated with cell activation.

Dissociation between the expression of IL 2 receptor and IL 2 receptor mRNA in the antigen-specific T cell clone stimulated by the specific antigen with B cell APC.

An antigen-presenting capacity of B cells was analyzed in comparison with that of whole spleen cells in terms of IL 2R expression of a human IgG-specific T cell clone, 24-2C.3. When the clone was stimulated with the antigen and irradiated spleen cells, the clone expressed an adequate amount of IL 2R on the surface in flow cytometric analysis. On the other hand, the clone expressed the receptor only poorly, being stimulated with B cell APC. The findings were confirmed by Western blot analysis on the clone solubilized by Nonidet P-40 and also by fluorescent antibody technique on the fixed clone. 24-2C.3 clone stimulated with B cell APC was also suggested not to secrete IL 2R in culture medium. In dot blot hybridization analysis performed with cDNA probe, however, 24-2C.3 clone stimulated with B cell APC was shown to express a comparable amount of IL 2R mRNA to the clone stimulated with whole spleen cells as APC. The mRNA expressed in the clones stimulated with B cells and with spleen cells could not be distinguished from each other in Northern blot analysis. The culture supernatant of 24-2C.3 clone incubated with the antigen and irradiated spleen cells was shown to enhance the expression of IL 2R on the clone stimulated with B cell APC. These results suggest that there is some defect in the antigen-presentation capacity of B cells in terms of the elicitation of the intracellular signal for IL 2R expression in T cells and that the humoral factor(s) produced in the presence of splenic adherent cells could supply the defect.

Expression of interleukin 2, interferon-gamma, and the IL 2 receptor by human peripheral blood lymphocytes.

Human peripheral blood T lymphocytes were treated with recombinant interleukin 2, mitogens, and dexamethasone. The resulting accumulation of mRNA for interleukin 2 (IL 2), the interleukin 2 receptor (IL 2R), and interferon-gamma (IFN-gamma) was measured. IL 2 was found to regulate the levels of each of these mRNA. The expression of mRNA for IL 2, IL 2R, and IFN-gamma correlated very well with the levels of protein observed. In populations of peripheral blood T lymphocytes, the production of IL 2 and IFN-gamma were not necessarily coordinately expressed. The sequential expression of these mRNA was investigated in order to determine whether they might be independent of the action of IL 2. IFN-gamma and IL 2 mRNA showed biphasic accumulations. IL 2 mRNA accumulated very rapidly, within 60 min after mitogen stimulation and before any detectable IL 2R mRNA accumulation. Similarly, IFN-gamma mRNA accumulated rapidly, simultaneously with IL 2 mRNA. This early peak of IFN-gamma mRNA, therefore, is likely to be independent of IL 2 action. Both IL 2 and IFN-gamma mRNA then showed later peak times of accumulation. IL 2 mRNA levels peaked at 5 hr after mitogen stimulation, whereas IFN-gamma mRNA levels peaked at 20 hr. IL 2R mRNA continued to accumulate for the full 40 hr of these kinetic experiments. The later accumulations of IFN-gamma and IL 2R mRNA and the resulting expression of the corresponding proteins may therefore be dependent on the earlier production of IL 2 and its subsequent interaction with the IL 2R on the surface of such activated T cells.