Studies on the pathogenesis of fever. 18. Activation of leukocytes for pyrogen production

A pre-formed Pyrogenic Factor Released by Lipopolysaccharide Stimulated Macrophages

The aim of this study was to investigate the pyrogenic activity of factor(s) released by rat peritoneal macrophages following a brief stimulation with LPS. The effect of this factor on the number of circulating leukocytes and serum Fe, Cu and Zn levels, was also evaluated. The possibility that the content of interleukin (IL)-1β, IL-6 and tumour necrosis factor (TNF) in the supernatant could explain the observations was investigated. Supernatant produced over a period of 1 h by peritoneal macrophages, following a 30 min incubation with LPS at 37°C, was ultrafiltered through a 10 000 MW cut-off Amicon membrane, sterilized, and concentrated 2.5, 5, 10 and 20 times. The intravenous (i.v.) injection of this supernatant induced a concentration-dependent fever in rats with a maximal response at 2 h. The pyrogenic activity was produced by macrophages elicited with thioglycollate and by resident cells. The supernatants also induced neutrophilia and reduction in Fe and Zn 6 h after the injection. Absence of activity in boiled supernatants, or supernatants from macrophages incubated at 4°C with LPS, indicates that LPS was not responsible for the activity. In vitro treatment with indomethacin (Indo), dexamethasone (Dex), or cycloheximide (Chx) did not modify the release of pyrogenic activity into the supernatant or its effects on the reduction in serum metal levels. Although Chx abolished the production of mediator(s) inducing neutrophilia, and Dex reduced the induction of IL-1β, TNF and IL-6, injection of the highest concentration of these cytokines detected in the supernatants did not induce fever. In vivo treatment with Dex, but not Indo, abolished the fever induced by the supernatant. These results suggest that macrophages contain pre-formed pyrogenic mediator(s), not related to IL-1β, IL-6 or TNF, that acts indirectly and independently of prostaglandtn. It also seems likely that the pyrogenic activity is related to the factor responsible for the reduction of serum Fe and Zn levels, but not the neutrophilia.

The Effect of IFN-gamma, Alum and Complete Freund Adjuvant on TNP-KLH Induced Ig.G(1), IgE and IgG(2a) Responses in Mice

Adjuvants are considered to play an important role in directing the isotype and amount of antibodies produced upon immunization by conducting the development of either Th-1 or Th-2 cells upon T-cell stimulation. This is based on the different cytokine production patterns that were observed after in vitro resttmulation of T cells isolated from mice immunized with antigen either adsorbed on alum or emulsified in complete Freund adjuvant (CFA). However, other studies suggest that primarily the type of antigen determines which isotypes are produced and to what extent. In these studies, however, IgE was not determined. Therefore, this study examined whether alum and CFA influenced the amount and/or ratio of IgG₁, IgE and IgG_2a produced after TNP-KLH immunization. Similar levels of IgG₁, IgE and IgG_2a antibodies were found upon immunization with TNP-KLH either adsorbed on alum or emulsified in CFA. Moreover, administration of IFN-γ in combination with TNP-KLH adsorbed on alum did not increase the amount of IgG_2a produced. IFN-γ treatment resulted in an increased IL-6 and decreased IFN-γ production by spleen cells upon Con A stimulation, whereas it did not change the IL-4 production in similar conditions. The presented results suggest that upon immunization with TNP-KLH high IL-4 levels are produced, resulting in an antibody response that is dominated by IgG₁, independent of the adjuvant employed. The IL-4 inducing property of TNP-KLH is substantiated by the finding that repeated immunization of mice with TNP-KI, without adjuvant, increases the serum total IgE level. The presented data suggest that the carrier part of TNP-KLH preferentially results in Th-2 cell activity after which the adjuvant merely enhances the antibody responses generated.

A comparative ultrastructural study of virions in human pre-AIDS and simian AIDS

Virions resembling the AIDS-associated retroviruses HTLV-III and LAV were identified between pseudopods of dendritic reticulum cells in lymph nodes from 3 patients with prodromal AIDS. The virions are morphologically distinguishable from HTLV-I and HTLV-II and also from D-type retroviruses that are associated with the simian acquired immune deficiency syndrome. Budding forms resembling incomplete nucleoids of maturing D-type retrovirus were found in neutrophils in a lymph node from another patient with prodromal AIDS. The significance of these structures is unknown.

Etiology of rheumatoid arthritis

The major thesis of the proposed hypothesis is that in the absence of microbial material synovial macrophages in rheumatoid arthritis patients continue to release interleukin 1, which perpetuates the inflammation so characteristic of the disease. Its release is suggested to result from an altered synovial macrophage glutathione metabolism brought about by the action of interleukin 1 on host copper metabolism. Three anti-rheumatic drugs are suggested to act at different points in this pathogenic chain reaction. Alclofenac on interleukin 1, gold thiolates on copper-inhibited macrophage glutathione reductase, and D-penicillamine on IgC catabolism. Drawing upon the hypothesis some suggestions are made for drug design.

Differences in pyrogen production by mononuclear phagocytes and by fibroblasts or HeLa cells

Phagocytosis of bacteria stimulates "professional" phagocytes to produce and release endogenous pyrogen (EP), the protein that mediates fever. To determine whether "nonprofessional" phagocytes also have this capacity, mouse and human fibroblasts and HeLa cells were cultured after ingestion of latex or chicken erythrocytes (CE), and EP release into culture supernate measured by mouse assay. No detectable pyrogen was released by these cell types after phagocytosis, whereas both latex and CE stimulated EP production by cultured mouse macrophages. These studies support the hypothesis that only professional phagocytes of bone marrow origin synthesize EP and induce fever.

On the mechanism of pyrogenic action of ricin

The incubation of rabbit white blood cells with ricin, the toxic protein of castor oil seeds, leads to the production of endogenous pyrogens. This induction can be inhibited by the antibiotics actinomycin D or cycloheximide. The results are discussed in terms of disturbed corticosteroid- and Mg2+-levels.

Colchicine stimulation of pyrogen production by human blood leukocytes

The effect of colchicine, an anti-inflammatory agent, on endogenous pyrogen (EP) production by human blood leukocytes in vitro was examined. Colchicine not only failed to suppress EP production by human leukocytes stimulated by phagocytosis, but, in the absence of other stimuli, micromolar concentrations of the drug induced pyrogen production and release by both polymorphonuclear (PMN) and mononuclear leukocytes. The response was dose related, occurring at concentrations above 0.1 muM. Colcemid and vinblastine, other agents which bind to microtubular protein, also induced pyrogen release from human leukocytes, whereas lumicolchicine, a light-alerted derivative of colchicine without affinity for microtubules, was ineffective. Colchicine did not induce EP production by rabbit leukocytes, even at 100 muM concentration. Studies of the mechanism of PMN leukocyte activation by Colcemid indicated that although the time required for contact between drug and leukocyte was brief, pyrogen production and release did not begin for 6 or more hours. If added during this time, puromycin prevented subsequent production and release of pyrogen. These results indicated that agents which interfere with the assembly of microtubules induce EP production and secretion by human leukocytes in vitro.

Studies on the mechanism of endogenous pyrogen production. III. Human blood monocytes

The characteristics of pyrogen production and release by human blood monocytes were investigated. A dose-response assay of monocyte pyrogen in rabbits indicated a linear relationship of temperature elevation to dose of pyrogen at lower doses. Monocytes did not contain pyrogen when first obtained, nor did they release it spontaneously even after 5 days of incubation in vitro. Pyrogen production was apparent 4 h after stimulation by endotoxin or phagocytosis, and continued for 24 h or more. Puromycin, an inhibitor of protein synthesis, prevented both initiation and continuation of pyrogen production and release. Pyrogen-containing supernates retained most pyrogenic activity during overnight incubation even in the presence of activated cells. Lymphocytes appeared to play no role in either initiation or continuation of pyrogen production in these studies.

Pyrogen release in vitro by lymphoid tissues from patients with Hodgkin's disease

The mechanism of fever in patients with Hodgkin's disease was investigated by examining endogenous pyrogen production by blood, spleen, and lymph node cells incubated in vitro. Blood leucocytes from febrile or afebrile patients with Hodgkin's disease did not produce pyrogen spontaneously. Spleen cells, however, frequently released pyrogen during initial incubations, unlike spleen cells from patients with non-malignant diseases. Pyrogen production occurred from spleens without observed pathologic infiltrates of Hodgkin's disease. Lymph nodes involved with Hodgkin's disease produced pyrogen more frequently than did nodes involved with other diseases. Pyrogen production by tissue cells was prolonged, required protein synthesis, and in some cases was due to mononuclear cells; it did not correlate with fever in the patient. These studies demonstrate spontaneous production of endogenous pyrogen in vitro by lymphoid tissue cells from patients with Hodgkin's disease.

Synthesis of endogenous pyrogen by rabbit leukocytes

Rabbit ieukocytes from peritoneal exudates and from blood were stimulated to form leukocyte pyrogen in the presence of radiolabeled amino acids. The stimuli used were endotoxin, phagocytosis, and tuberculin. The crude leukocyte pyrogen samples were purified; pyrogen from exudate cells was rendered homogeneous; pyrogen from blood cells was still contaminated with other proteins. All the purified pyrogens were radioactive; and for all it was shown that radioactivity and pyrogenic activity coincided on electrophoresis at pH 3.5 and pH 9 in acrylamide and on isoelectric focusing in acrylamide. Furthermore, pyrogens obtained from exudate cells stimulated in different ways, or from blood cells and exudate cells stimulated with endotoxin, appeared to be identical. These results suggest that leukocyte pyrogen was synthesized de novo from amino acid precursors and that leukocytes made the same pyrogen whatever the stimulus used to activate them.

Studies on the mechanism of fever accompanying delayed hypersensitivity. The role of the sensitized lymphocyte

Experiments have been carried out to investigate the possible role of the sensitized lymphocyte in mediating the fevers of delayed hypersensitivity. Rabbits were made delayed hypersensitive to one of several heterologous proteins (bovine gamma globulin, bovine serum albumin, or human serum albumin) by footpad injection of antigen or antigen conjugated with dinitrophenol and incorporated in complete Freund's adjuvant. At intervals after sensitization, various tissues were removed, and single cell suspensions were incubated overnight with either carrier protein or conjugate in vitro. Release of an endogenous pyrogen (EP) was assayed by intravenous injection of the supernatant fluid into unsensitized rabbits. Of the tissues tested only those containing both lymphocytes and pyrogen-producing cells, blood, spleen, and draining lymph nodes, released detectable amounts of EP when incubated with antigen in vitro. Incubation of normal blood cells with specifically sensitized lymphocytes and antigen also resulted in significant release of pyrogen. Similarly, blood leukocytes released EP in vitro after mixture with supernates derived from incubation of sensitized lymphocytes and antigen. Cells and supernatant fluids from draining lymph nodes were usually effective in activating normal blood leukocytes earlier after sensitization than were those from mesenteric lymph nodes, suggesting that such cells, or antigen, had migrated from the original site of sensitization. The activator was soluble, nonpyrogenic in the dosages tested, and required incubation of viable cells with specific antigen for its production. These properties suggest that it may belong to the class of "lymphokines," biologically active agents released from lymphocytes that have been activated by immunologic or certain nonimmunologic stimuli.

Studies on the pathogenesis of fever. XX. Suppression and regeneration of pyrogen-producing capacity of exudate granulocytes

Suppression of the pyrogen-producing capacity of exudate granulocytes results from incubation of the cells in plasma, serum, or Ringer's solution. When transferred in this state and incubated in isotonic NaCl, the cells release much less pyrogen than untreated exudate cells. The suppressive effect is reversible and appears to involve the cellular uptake of calcium ions. In contrast, regeneration of pyrogen-producing capacity in depleted exudate cells occurs only when the cells are incubated in serum. The process resembles activation and requires the cellular synthesis of protein.

Studies on the pathogenesis of fever. XIX. Localization of pyrogen in granulocytes

Only intact exudate granulocytes from rabbits generated large amounts of endogenous pyrogen when incubated in 0.15 M NaCl. No matter how whole-cell lysates or combinations of subcellular fractions were incubated, their yields of pyrogen never approached those of whole cells; at most, only minimal amounts of pyrogen were formed, once the integrity of the cells had been destroyed. Some pyrogen could be extracted from disrupted cells, but never more than a fraction (<25%) of that released from incubated whole cells. The yield could be slightly improved by lowering the pH (to 3.5) and by increasing the volume of extraction fluid. Virtually all of the preformed pyrogen that could be extracted from sucroselysed cells was found in their cytoplasmic fraction. Contrary to the results of Herion et al. (3), none could be detected in the granular (or lysosomal) fraction. Likewise, all efforts to recover pyrogen from the membrane-nuclear fraction were unsuccessful. In keeping with the finding that preformed pyrogen is contained in the cytoplasmic fraction were the observations that practically all of the aldolase, a cytoplasmic enzyme, and very little of the acid phosphatase, a granular enzyme, were lost from the cells during the release of pyrogen. Lysozyme, an enzyme stored in both the granules and the cytoplasm, was partially released from the cells under the same circumstances. Neither the release of pyrogen nor its slight intracellular buildup that precedes release (4) were affected by concentrations of puromycin that block protein synthesis in the cells and prevent their activation. Hence, it is concluded that the release process, which also involves the formation of active pyrogen (4), does not require protein synthesis, whereas activation of the cells, which may involve the synthesis of an inactive precursor (2), does.

Studies on the origin of human leukocytic pyrogen

Release of the protein molecule, leukocytic pyrogen, is one of the many reactions exhibited by leukocytes after phagocytosis. After the ingestion of heat-killed S. albus, a 3-4 hr latent period exists, during which human peripheral leukocytes release no pyrogen, yet cellular metabolism is altered in such a way that pyrogen output may subsequently occur in the absence of further phagocytosis. Transcription of messenger RNA and translation of new protein are initial events in the. activation process, since addition of the inhibitors, actinomycin D, and cycloheximide or puromycin, during this period markedly depressed or abolished subsequent pyrogen release. These effects were noted to be dependent upon the time of addition of the inhibitors. None of the inhibitor drugs interfered with cell viability as measured by phagocytosis and hexose monophosphate shunt activity, nor did they alter the pyrogenicity of preformed leukocytic pyrogen. Vincristine did not inhibit pyrogen formation, consistent with its reported failure to alter RNA synthesis in mature human granulocytes. The glycolytic inhibitor, sodium fluoride, blocked pyrogen release both when added prior to particle ingestion or 1 hr after the initiation of phagocytosis. Whereas inhibition of phagocytosis would explain the sodium fluoride effect prior to 1 hr, this was not observed in leukocyte preparations incubated for 1 hr with S. albus before adding sodium fluoride. When sodium fluoride was added to preparations 2 hr after the start of incubation, the LP production was unimpaired. Potassium cyanide had no effect on cell activation or pyrogen release. These findings suggest that the primary energy supply for the activation process is derived from high energy phosphate bonds provided by anaerobic glycolysis. Since the major amount of cell activation appears to occur in the 1st hr after phagocytosis, this energy might be involved in the induction of a genome leading to the transcription of m-RNA and its translation into new protein or is required for polysome integrity during protein synthesis. It is suggested that this new protein may be leukocytic pyrogen itself, or an enzyme responsible for cleaving it from an inactive precursor.

Studies on the pathogenesis of fever. XVII. The cationic control of pyrogen release from exudate granulocytes in vitro

Evidence has been presented that the release of active endogenous pyrogen from rabbit exudate granulocytes incubated in isotonic NaCl is a relatively prompt energy-dependent process that is preceded by a rise in intracellular pyrogen, and involves a rise in total intracellular cations and an increased permeability of the cell membranes, but does not require the synthesis of new proteins.