Binding and internalization of the 163-171 fragment of human IL-1 beta

The mechanisms of cell association of the human interleukin (IL-1 beta) immunostimulatory fragment 163-171 have been studied. The fragment was able to associate abundantly to both IL-1R- and IL-1R+ cells. Binding was strictly temperature dependent, was not saturable and could be inhibited by excess amounts of unlabelled 163-171 peptide but not by IL-1 beta, suggesting that the 163-171 fragment is not an IL-1R-binding domain of IL-1 beta. The fragment is readily internalized by cells by a cytochalasin-insensitive mechanism and it localizes mainly in the cytoplasm. It is concluded that the active domain 163-171 of IL-1 beta can be taken up by cells through a receptor-independent, temperature-dependent mechanisms and that its ability to activate cellular functions is based on IL-1R-independent intracellular pathways.

Binding of IL-1 beta to IL-1R type II at single cell level

To gain information on the possible biologic role of IL-1R type II (IL-1RII), expression of the 68-kDa IL-1 binding protein on human lymphoblastoid B cells was investigated at single cell level. Binding of iodinated IL-1 beta was evaluated by autoradiography on cytosmears of IL-1RII positive B cell lines RAJI, the RAJI clone 1H7, and STS 25. Results obtained suggest an heterogeneity of IL-1RII expression within the B cell population, with only 5 to 16% of the cells able to bind IL-1 beta. Up-regulation of IL-1RII expression by dexamethasone, evident in conventional binding assays, was achieved through both increase in the number of IL-1 binding cells (14-30%) and augmentation of receptor density on positive cells, By combining autoradiography with immunocytochemical staining, it could be shown that about 80% of IL-1RII + cells were negative for Ki67, a nuclear antigen expressed from late G1 to M phase. Cell cycle dependent expression of IL-1RII was confirmed on cells enriched in different phases of the cell cycle by counterflow centrifugal elutriation. It is thus proposed that IL-1RII is associated to the cell cycle.

Binding of IL-1 beta to IL-1R type II at single cell level

To gain information on the possible biologic role of IL-1R type II (IL-1RII), expression of the 68-kDa IL-1 binding protein on human lymphoblastoid B cells was investigated at single cell level. Binding of iodinated IL-1 beta was evaluated by autoradiography on cytosmears of IL-1RII positive B cell lines RAJI, the RAJI clone 1H7, and STS 25. Results obtained suggest an heterogeneity of IL-1RII expression within the B cell population, with only 5 to 16% of the cells able to bind IL-1 beta. Up-regulation of IL-1RII expression by dexamethasone, evident in conventional binding assays, was achieved through both increase in the number of IL-1 binding cells (14-30%) and augmentation of receptor density on positive cells, By combining autoradiography with immunocytochemical staining, it could be shown that about 80% of IL-1RII + cells were negative for Ki67, a nuclear antigen expressed from late G1 to M phase. Cell cycle dependent expression of IL-1RII was confirmed on cells enriched in different phases of the cell cycle by counterflow centrifugal elutriation. It is thus proposed that IL-1RII is associated to the cell cycle.

Quantitation of biologically active IL-1 by a sensitive assay based on immobilized human IL-1 receptor type II (IL-1RII)

A rapid and sensitive solid-phase radioassay is described for the quantitative detection of human interleukin-1 (IL-1) based on its capability to bind the nitrocellulose-immobilized IL-1 receptor solubilized from plasma membranes of a subclone of the human B cell lymphoma Raji. The assay can detect human IL-1 beta levels as low as 1 X 10(-11) M, both in physiological buffers and in human plasma. Much lower sensitivity was observed for human IL-1 alpha (3.7 X 10(-9) M) and murine IL-1 beta (2 X 10(-9) M). This assay has the advantage to specifically detect only the correctly folded biologically active IL-1. Simple pretreatment procedure that selectively removes IL-1 beta from samples has been devised so that the ratio of the two IL-1s isoforms in the sample can be precisely determined. This assay represents a fast method for the simultaneous-testing of large numbers of biological samples.

The effect of adrenalectomy on interleukin-1 release in vitro and in vivo

1 Peritoneal macrophages (M phi) collected from adrenalectomized (ADX) rats released more interleukin-1 (IL-1) activity and prostaglandin E2 (PGE2) than macrophages from sham-operated (SHO) rats. 2 The increase in IL-1 activity in the supernatants was confirmed by the increase of the cell-associated 33 kD IL-1 alpha precursor in ADX macrophages stimulated by lipopolysaccharide (LPS). 3 After the injection of Complete Freund's Adjuvant (CFA) to induce adjuvant arthritis, 60% of the ADX rats died, while no deaths occurred in the SHO group. 4 The in vivo administration of dexamethasone inhibited both IL-1 and PGE2 release by macrophages as well as protecting ADX animals from CFA-induced death. Indomethacin and BW 755C partially protected the animals from this lethal effect. 5 These results suggest that adrenalectomy induces an increased release of IL-1 both in vitro and in vivo, and are consistent with a feedback mechanism between IL-1 and glucocorticoid hormones.

A monoclonal antibody to the IL-1 beta peptide 163-171 blocks adjuvanticity but not pyrogenicity of IL-1 beta in vivo

The synthetic fragment VQGEESNDK, corresponding to the amino acid sequence in position 163-171 of human IL-1 beta, possesses the immunostimulatory but not the pyrogenic activity of the mature IL-1 beta polypeptide in vivo. To assess the relevance of this domain of IL-1 beta for its biologic activities, a mAb was raised against the synthetic peptide 163-171. The mAb Vhp20 could effectively recognize human rIL-1 beta in RIA and immunoblotting. In vivo, the mAb Vhp20 was able to selectively inhibit the immunostimulatory activity of IL-1 beta, but it could not affect the fever-inducing capacity of IL-1 beta. It is proposed that functional domains could be identified in the human IL-1 beta protein and that the fragment in position 163-171 is of major importance for the adjuvant capacity of the entire molecule, but irrelevant to its pyrogenic activity.

A monoclonal antibody to the IL-1 beta peptide 163-171 blocks adjuvanticity but not pyrogenicity of IL-1 beta in vivo

The synthetic fragment VQGEESNDK, corresponding to the amino acid sequence in position 163-171 of human IL-1 beta, possesses the immunostimulatory but not the pyrogenic activity of the mature IL-1 beta polypeptide in vivo. To assess the relevance of this domain of IL-1 beta for its biologic activities, a mAb was raised against the synthetic peptide 163-171. The mAb Vhp20 could effectively recognize human rIL-1 beta in RIA and immunoblotting. In vivo, the mAb Vhp20 was able to selectively inhibit the immunostimulatory activity of IL-1 beta, but it could not affect the fever-inducing capacity of IL-1 beta. It is proposed that functional domains could be identified in the human IL-1 beta protein and that the fragment in position 163-171 is of major importance for the adjuvant capacity of the entire molecule, but irrelevant to its pyrogenic activity.

Differential binding of IL-1 alpha and IL-1 beta to receptors on B and T cells

The interleukin 1 receptors (IL-1R) on the human B lymphoma RAJI and on the murine thymoma EL4-6.1 have been characterized. Equilibrium binding analysis using both 125I-labeled IL-1 alpha and IL-1 beta showed that RAJI cells have a higher number of binding sites/cell for IL-1 beta (2400, Kd 2.2 nM) than for IL-1 alpha (316, Kd 0.13 nM). On the other hand, EL4-6.1 cells have more receptors/cell for IL-1 alpha (22 656, Kd 1 nM) than for IL-1 beta (2988, Kd 0.36 nM). Dexamethasone (DXM) induced on RAJI cells a time-dependent increase in binding sites for both IL-1 beta and IL-1 alpha without affecting their binding affinities. However, while receptor-bound 125I-IL-1 alpha was displaced with equal efficiency by both IL-1 forms, only unlabeled IL-1 beta could effectively displace 125I-IL-1 beta. Cross-linking experiments indicated that RAJI cells have a predominant IL-1R of about 68 kDa, while EL4-6.1 cells have an IL-1-binding polypeptide of 80 kDa. These results suggest that B and T cells possess structurally different IL-1R with distinct binding properties for IL-1 alpha and IL-1 beta.

Cytoskeletal alterations as a parameter for assessment of toxicity

1. Some environmental substances, drugs and pollutants affect the growth of cultured cells, and produce cytoskeletal alterations. 2. These have been used as parameters for toxicity assessment of cholera toxin and pertussis toxin in Chinese Hamster Ovary cells. 3. Cholera toxin stabilized microtubules and had no effect on microfilaments and intermediate filaments. 4. Pertussis toxin affected microfilaments but appeared to have no effect on microtubules and intermediate filaments.

In vitro generated mast cells express natural cytotoxicity against tumour cells

Bone marrow cells from mice were cultured in vitro in the presence of interleukin-3 (IL-3). After 2 weeks, the majority of the cells differentiated towards mast cells as judged by morphological and biochemical criteria. When populations of 99% IL-3-dependent mast cells (IL-3 MC) were tested for their anti-tumour activity in vitro, it was found that they can express natural cytotoxicity (NC) but not other natural reactivities. Moreover, the effector cells were not positive for Thy 1, Lyt 1 and Lyt 2 markers. The capability of mast cells to express NC activity seems to be related to their in vitro differentiation, since mast cell deficient W/Wv mice had normal NC activity. Thus, IL-3 MC must be added to the variety of cells capable of expressing natural anti-tumour reactivities in vitro.

Interferon inhibits prostaglandin biosynthesis in macrophages: effects on arachidonic acid metabolism

Mouse resident peritoneal M phi produced considerable amounts of PGE when triggered in vitro with soluble or particulate stimuli. Preexposure of M phi to IFN-beta dramatically decreased PGE production. This effect depended on the dose of IFN-beta used and was abolished by anti-IFN-beta globulin. In addition to PGE, other AA metabolites of the cyclooxygenase pathway, namely TXB2 and 6-keto PGF1 alpha, were decreased in IFN-beta-treated M phi. However, IFN-beta did not have any effect on cyclooxygenase activity of M phi, indicating that an earlier step of PG biosynthesis was likely to be the target of its inhibitory action. Indeed, the release of radioactive compounds from M phi prelabeled with [14C]AA was strongly impaired by IFN-beta, suggesting that IFN-beta would decrease PG production in M phi by blocking phospholipase activation. The possibility that the IFN-beta effect on phospholipase could be mediated through the increase of the intracellular levels of cAMP is suggested.

Interferon inhibits prostaglandin biosynthesis in macrophages: effects on arachidonic acid metabolism

Mouse resident peritoneal M phi produced considerable amounts of PGE when triggered in vitro with soluble or particulate stimuli. Preexposure of M phi to IFN-beta dramatically decreased PGE production. This effect depended on the dose of IFN-beta used and was abolished by anti-IFN-beta globulin. In addition to PGE, other AA metabolites of the cyclooxygenase pathway, namely TXB2 and 6-keto PGF1 alpha, were decreased in IFN-beta-treated M phi. However, IFN-beta did not have any effect on cyclooxygenase activity of M phi, indicating that an earlier step of PG biosynthesis was likely to be the target of its inhibitory action. Indeed, the release of radioactive compounds from M phi prelabeled with [14C]AA was strongly impaired by IFN-beta, suggesting that IFN-beta would decrease PG production in M phi by blocking phospholipase activation. The possibility that the IFN-beta effect on phospholipase could be mediated through the increase of the intracellular levels of cAMP is suggested.