Takashi Ikejima

Interleukin 1 induces a shock-like state in rabbits. Synergism with tumor necrosis factor and the effect of cyclooxygenase inhibition.

In addition to activating T and B lymphocytes, interleukin 1 (IL-1) induces several hematologic and metabolic changes typical of host responses to infection and injury. We now report a new biological property, namely, the induction of hypotension. Rabbits given a single intravenous injection of recombinant human IL-1-beta (5 micrograms/kg) rapidly developed decreased systemic arterial pressure, which reached the lowest levels after 50-60 min and slowly returned to pre-IL-1 values after 3 h. Associated with the hypotension, systemic vascular resistance and central venous pressure fell, while cardiac output and heart rate increased. These responses were prevented by ibuprofen given 15 min before the IL-1. A bolus injection of IL-1 followed by a 2-h infusion sustained the hypotension and was associated with leukopenia and thrombocytopenia. Ibuprofen given at the mid-point of the infusion reversed the changes in all hemodynamic parameters, but had no effect on the leukopenia or thrombocytopenia. Tumor necrosis factor (TNF) also induced a shock-like state in rabbits. When the dose of IL-1 or TNF was reduced to 1 microgram/kg, no hemodynamic changes were observed; however, the combination of these low doses of both cytokines resulted in a profound shock-like state including histological evidence of severe pulmonary edema and hemorrhage. Pretreatment with ibuprofen prevented the hemodynamic, leukocyte, and platelet changes induced by the low-dose cytokine combination, and ameliorated the pulmonary tissue damage. These results demonstrate that IL-1, like TNF, possesses the ability to induce hemodynamic and hematological changes typical of septic shock, and that the combination of IL-1 and TNF is more potent than either agent alone. These effects seem to require cyclooxygenase products, and suggest that intravenous cyclooxygenase inhibitors may be of therapeutic value in patients with IL-1/TNF-mediated shock.

Concentrations of immunoreactive human tumor necrosis factor alpha produced by human mononuclear cells in vitro

The concentrations of tumor necrosis factor (TNF) produced by human peripheral blood mononuclear cells (MNC) were measured using a radioimmunoassay (RIA) for human TNF. This was developed using a rabbit antiserum against human recombinant TNF (Hu rTNF), and Hu rTNF labeled with Na1251 by a modification of the chloramine T method. This RIA does not detect human lymphotoxin, interieukin‐1 alpha or beta, interleukin 2, interleukin 6, interferon alpha or gamma, granulocyte‐macrophage‐colony stimulating factor, and C5a des arg. A good correlation (r = 0.89) was found between the RIA and the cytolytic bioassay for TNF. The sensitivity of the RIA is between 3 and 78 pg/ml (median 11 pg/ml).

Induction of human interleukin-1 by a product of Staphylococcus aureus associated with toxic shock syndrome.

Certain strains of Staphylococcus aureus associated with toxic shock syndrome elaborate material that induces human blood monocytes to secrete interleukin-1 (IL-1). IL-1 was detected both by its ability to cause fever in rabbits using the leukocytic pyrogen (LP) assay and by its mitogenic activity towards thymocytes in the so-called lymphocyte-activating factor (LAF) assay. Anti-human IL-1 prevents the manifestation of both activities. Filtrates of control strains of S. aureus manifest neither activity. Thus, culture filtrates derived from toxic shock syndrome (TSS)-associated strains cause biphasic fever in rabbits when injected intravenously. The fever lasts several hours. Plasma taken at the peak of the fever and injected into a second set of rabbits produces a brief monophasic fever typical of LP. Further, human monocytes release LP when incubated with TSS filtrates in vitro. The monocyte products also stimulate the proliferation of mouse thymocytes in the presence of phytohemagglutinin in a manner characteristic of LAF. A bacterial filtrate is much less effective without an intermediate incubation with monocytes. The stimulation of monocyte IL-1 production is easily quantified, provides a simple method of assaying the TSS toxin, and since it involves human cells, is directly relevant to the human disease. The assay was used to monitor the purification of TSS toxin. Only 0.1 ng/ml of the purified material is required to induce monocyte IL-1 production. It is thus more potent than endotoxin. In contrast to endotoxin, its effect is not blocked by polymyxin B. We conclude that in TSS the sudden fever and probably other components of the acute phase response may be attributed to a massive release of IL-1.

Studies on IL-1 receptors on D10S T-helper cells: Demonstration of two molecularly and antigenically distinct IL-1 binding proteins

Receptor binding studies were performed on the interleukin-1 (IL-1) sensitive T-helper cell line D10S, a stable line which proliferates to subfemtomolar concentrations of IL-1 in the absence of mitogens. IL-1 binds in a specific and saturable manner and Scatchard analysis at 4 degrees C reveals one class of binding affinity. On D10S cells, the Kd for IL-1 is 227 pM +/- 80, with 11,000 (range 3,300 to 23,800) sites per cell. EL4.6.1 cells, which are less sensitive to IL-1, bind with a single class of high affinity sites (55 pM; 4,000 sites). D10S cells incubated 18 h with IL-1 display reduced IL-1 receptor (IL-1R) numbers and affinities, consistent with reduced (75%, p less than 0.005) proliferation to subsequent IL-1; preincubation with IL-4 increases the number of IL-1R which is associated with increased (200%, p less than 0.001) proliferation to IL-1. The molecular mass of the major (80 kD) IL-1R binding [125I]IL-1 alpha on D10S cells was consistently observed at 73 kD as compared to the 80 kD molecule on the EL4 cells. On the other hand, crosslinking studies with [125I]IL-1 beta on D10S cells revealed a novel 46 kD band on gradient SDS-PAGE corresponding to a binding protein of 29 to 30 kD, which is antigenically distinct from the 80 kD IL-1R. Crosslinking of D10S or EL4 cells at 4 degrees C in the presence of phytohemagglutinin (PHA) and labeled IL-1 enhanced the appearance of the 30 kD IL-1 binding protein. The findings are consistent with a two-chain model for the IL-1R, although Scatchard analysis did not consistently indicate two classes of affinities. IL-1 binding to the 80 kD protein may form a heteroduplex with the 30 kD IL-1R which could account for the presence of the 120 to 130 kD IL-1 crosslinked proteins observed by several investigators.