The role of the colony-stimulating factors in resistance to acute infections

Leishmania donovani amastigote components-induced colony-stimulating factors production

Increased hematopoiesis, driven by colony-stimulating factors (CSFs), is known to occur in infectious diseases. However, whether Leishmania donovani component(s) can directly induce the synthesis and secretion of CSFs is not known. We report that L. donovani amastigote antigens soluble in culture medium (LDAA; 0.01-10 mg/kg), injected intravenously in BALB/c mice, induced the production of serum CSFs; maximum induction (128>16 colonies) occurred at 1 mg/kg. In vitro also, LDAA (0.01-1 mg/ml) induced mouse peritoneal macrophages (MØs) to elaborate CSFs in the conditioned medium (CM); 0.1 mg/ml LDAA appeared optimal (68+/-9 colonies). Both in vivo and in vitro, the kinetics of CSF production were similar with peak response occurring 24 h after stimulation and return to background levels by 72 h. A predominant approximately 12 kDa LDAA protein (LDAA-12) also induced CSF production, both in serum and CM, in a dose-and time-dependent manner. Rabbit anti-LDAA-12 antibody significantly (p<0.05) reduced both the LDAA-and LDAA-12-induced CSF production, in vitro. Functionally, the LDAA-12-induced CSFs, both in the serum and CM, appeared to be similar as they supported the formation of granulocyte (G), MØ (M) and GM colonies, in vitro, in similar proportion; GM colonies were maximum (>80%). Further, LDAA-12 induced significantly (p<0.05) high GM-CSF levels both in serum and CM (19+/-3 and 15+/-2 ng/ml, respectively), as compared to the controls. Neutralizing (100%) goat anti-mouse tumour necrosis factor-alpha (TNF-alpha) immunoglobulin G did not affect the LDAA-12-induced CSF production by MØs, indicating it to be TNF-alpha-independent. LDAA-12 induced de novo CSF production, as MØs co-treated with LDAA-12 and cycloheximide (50 microg/ml) did not elaborate CSFs. The CSF-inducing capability of LDAA-12 appeared to be heat (70 C; 1 h)-labile, destroyed by proteases (pronase E and trypsin) and was unaffected by sodium periodate treatment. In LDAA-12-treated mice, the splenic and femur colony forming unit-GM counts showed a maximum of 2.2- and 1.9-fold increase, respectively, as compared to the controls. These data are the first to directly demonstrate that L. donovani amastigote components can induce the production of CSFs that may play important role(s) in the pathogenesis of visceral leishmaniasis.

Neutrophil modulation of the pulmonary chemokine response to lipopolysaccharide

When cells within the intrapulmonary compartment are exposed to pathogens or their products such as lipopolysaccharide, they produce CXC chemokines in order to attract circulating neutrophils into the lower respiratory tract. Previous studies have shown that as neutrophils (PMNs) enter the lung, bronchoalveolar lavage (BAL) chemokine levels are decreased. In this study, we determined the intrapulmonary and systemic responses to two important rat chemokines, cytokine-induced neutrophil chemoattractant (CINC) and macrophage inflammatory protein-2 (MIP-2), to intratracheal (i.t.) LPS (100 microg in 0.5 mL of phosphate-buffered saline) under neutropenic (cyclophosphamide [CPA]) and neutrophilic (G-CSF) conditions. By 4 h after i.t. LPS, CPA pretreatment decreased PMN recruitment 83% and G-CSF increased PMN recruitment 91% compared with recruitment into the lung in vehicle-pretreated rats (42.7 +/- 19.3 million PMNs). Neutropenic rats had increased CINC and MIP-2 concentrations in BAL fluid 4 h after i.t. LPS when compared with levels seen in vehicle controls (P < 0.05). In vitro LPS-stimulated chemokine production by alveolar macrophages obtained from CPA- and vehicle-pretreated animals did not differ. The increase in BAL fluid chemokine levels in neutropenic rats corresponded to increased chemotaxis of neutrophils to BAL fluid from CPA-pretreated rats as compared with the chemotaxis response of PMN to BAL fluid from vehicle-pretreated rats. In contrast, G-CSF enhancement of neutrophil recruitment decreased chemotactic activity of BAL fluid collected 4 h after i.t. LPS. These data show that as neutrophils are recruited into the lung, they alter chemokine levels, which most likely serves to down-regulate the inflammatory response.

Induction and regulation of endogenous granulocyte colony-stimulating factor formation

Granulocyte colony-stimulating factor (G-CSF) is one of the most prominent endogenous proteins in broad clinical use. While its biological and clinical effects are relatively well studied, little is known about its endogenous formation in health and disease. However, such knowledge is crucial to decide in which situations G-CSF should be applied efficiently in the clinic, ie. when endogenous production does not suffice. The dramatic changes induced by G-CSF in the differential blood cell count are directly immunomodulatory, strengthening the innate defence by multiplying neutrophilic granulocytes. A multitude of further immunomodulatory effects contribute to the regulation of the concerted host defence. In this review, following a short introduction into the biology of G-CSF, the available data on endogenous formation in a number of animal models and human diseases is compiled. The cellular sources and inducers of G-CSF formation are reviewed and the regulation of G-CSF expression on both the transcriptional and translational level are discussed. The emerging understanding of the role and regulation of endogenous G-CSF formation opens up possibilities to define therapeutic windows as well as targets for diagnostics or drug development. Lastly, the modulation of G-CSF formation by various pharmacological agents alerts to putative side effects of these drug treatments.

Serum amyloid P-component-induced colony-stimulating factors production by macrophages

Purified mouse serum amyloid P-component (SAP; 0.5-50 microg/kg), injected intravenously into Swiss mice, induced the production of serum colony-stimulating factors (CSFs); the maximum induction was observed at 10.0 microg/kg. Further, in vitro purified mouse SAP (0.1-50 microg/ml) stimulated the mouse elicited peritoneal macrophages to elaborate CSFs in the conditioned medium (CM); 5.0 microg/ml SAP appeared to be the optimum. Both in vivo and in vitro the maximum production of CSFs occurred 6 h after initiation of stimulation, and returned to the background levels by 48 h. Mannose 6-P, mannose 1-P and mannose, and not other sugars inhibited the SAP-induced production of CSFs by macrophages which suggests that SAP interaction with macrophages was mediated by specific glycoprotein-receptors. A neutralizing (100%) concentration of rabbit antimouse interleukin (IL)-1 polyclonal antibody had no effect on the SAP-induced CSF production, indicating that it would be IL-1-independent. SAP-induced CSFs, both in serum and CM, were functionally similar as they supported the formation of granulocyte (G), macrophage (M) and GM colonies in similar proportions. The production of CSFs appeared to be lipopolysaccharide (LPS)-independent as it was not inhibited by polymyxin B sulfate (25.0 microg/ml), and heat-inactivated (80 degrees C, 1 h, pH 7.0) SAP did not induce the production of CSFs. The CSFs were produced de novo because cycloheximide (50.0 microg/ml) completely inhibited their production. These results demonstrate that purified mouse SAP, in a dose-dependent manner, can induce the production of serum CSFs in mice, and can induce LPS-independent de novo production of CSFs by elicited macrophages in vitro.

Cytokine response to group B streptococcus infection in mice

This study was undertaken to better understand the complex relationship between specific and non-specific host defence mechanisms and group B streptococci (GBS). A comprehensive kinetics analysis of cytokine mRNA expression was performed, by Northern blot assay, in peritoneal exudate cells (PEC) and spleen cells (SC) recovered from CD-1 mice at various times during the course of an intraperitoneal infection with a lethal dose (5 x 10(3) microorganisms/mouse) of type Ia GBS, reference strain 090 (GBS-Ia). Analysis of cytokines involved in the development of a specific TH response shows that GBS-Ia in PEC induce only a weak increase of IL-2 mRNA expression and in SC a cytokine pattern characterized by IL-2, IFN-gamma and IL-12 in the absence of IL-4, IL-5 and IL-10. This selected cytokine pattern could provide appropriate conditions for the development of a TH1 response. Analysis of inflammatory cytokines, which are usually induced early during an in vivo infection, shows that there is a significant expression of mRNA specific for IL-1beta, TNFalpha and IL-6, both in PEC and SC only at 24 h which persists at a high level until 36 h. This delayed cytokine induction, accompanied by the contemporary activation of splenic phagocytic cells, occurs only when the number of GBS-Ia is extremely high. In fact, at 24 h GBS-Ia have heavily colonized all organs. In vitro infection of thioglycollate-elicited peritoneal macrophages confirms that the ability of GBS-Ia to induce a strong inflammatory cytokine response depends strictly on the number of infecting microorganisms. Indeed, macrophages respond to GBS-Ia with a very rapid induction of IL-1beta and TNFalpha mRNA when infected at a ratio of 1:10, but not at 100:1. Two major observations emerged from this study: (1) GBS-Ia, by inducing a cytokine pattern which seems to favour development of a TH1 response, could evade antibody production essential for resistance to GBS; and (2) inflammatory cytokine response is induced when a heavy microbial invasion of the host has already occurred. These novel features of GBS-Ia could contribute to the development and progression of lethal infection in mice.

The effect of GM-CSF and G-CSF on human neutrophil function

A direct comparison of GM-CSF and G-CSF in a panel of in vitro neutrophil-function assays was performed to investigate any differences in activity profiles. In our modified chemotactic assay, GM-CSF rapidly increased the migratory capacity of polymorphonuclear cells (PMNs) to move toward fMLP and LTB4. In contrast, G-CSF only stimulated PMN migration towards fMLP. GM-CSF, but not G-CSF, increased PMN cytotoxic killing of C. albicans blastospores. The expression of PMN surface antigens associated with Fc- and complement-mediated cell-binding (Fc gamma R1, CR-1 and CR-3), and adhesion signalling (ICAM-1), was increased after the exposure of GM-CSF, but not to G-CSF. In contrast these CSFs demonstrated relative equipotency in their ability to induce PMN anti-bacterial phagocytosis, and to restore the Staphylococcus aureus killing capacity of dexamethasone-suppressed neutrophils. The phagocytic activity of PMNs for opsonized yeast, as well as hexose-monophosphate shunt activity, was equivalent following GM-CSF or G-CSF treatment. We discuss the significance of the difference in activity profiles in this article.

Cytokines and progenitor cells of granulocytopoiesis in peripheral blood of patients with bacterial infections

To investigate the physiological role of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the adaptation mechanisms of myelopoiesis to enhanced demand, we studied both cytokines and their myeloid target cells in hematologically healthy patients suffering from acute bacterial infections. Endogenous serum levels of G-CSF and GM-CSF, granulocyte-macrophage colony-forming cell (GM-CFC) concentrations, and differential counts were determined for the peripheral blood of 57 patients with clinically apparent bacterial infections (26 males and 31 females aged 16 to 89 years) and 18 healthy controls (8 males and 10 females aged 23 to 84 years). Patients were selected for acute-phase protein and at least two additional clinical signs reflecting a bacterial infection. Patients showed significantly higher numbers of myeloid progenitor cells than controls (median, 68 versus 26 GM-CFC/ml; P < or = 0.01). G-CSF but not GM-CSF levels were found to be elevated (> or = 50 to 863 pg/ml). In the acute stage of infection, progenitor and cytokine levels were not influenced by gender, differences in therapy, or localization of the infection. Progenitor and G-CSF levels were not associated with absolute neutrophil counts or C-reactive protein. However, a negative correlation between number of GM-CFC per milliliter and age (R = -0.47; P < or = 0.001) and an inverse relationship between the incidence of high GM-CFC concentrations and elevated G-CSF levels (phi = -0.34; P < or = 0.01) were found. Combining both parameters into a cytokine-progenitor pattern, we observed a highly significant age-dependent response of myelopoiesis to inflammation (P < or = 0.001). Younger patients had high progenitor counts (> 75 GM-CFC/ml) associated with G-CSF levels below 50 pg/ml, whereas for the older patients, the reverse pattern was predominant. The results indicate that the age-dependent myelopoietic response to acute bacterial infections is characterized by an inverse relationship between progenitor cells and G-CSF. The observed cytokine-progenitor patterns could have implications for therapy with G-CSF and the prognosis of infectious diseases.

Cytokines in the treatment of leishmaniasis: from studies of immunopathology to patient therapy

The genus Leishmania, an obligate intramacrophage parasite, causes a wide spectrum of clinical diseases. It is worldwide in distribution and causes 20 million new cases annually with an at risk population of approximately 1.5 billion persons. The most severe forms are associated with high morbidity, mortality and relapses with conventional therapy. The therapeutic issues and responses to standard and alternative therapies are reviewed. Recent developments in molecular biology and immunology methods employed in the study of leishmaniasis have defined an intricate interaction of the parasite with host immune system. Perturbation of the host immune responses may be part of the survival mechanisms of Leishmania. In murine model, the finding of T helper cells that differ by their panel of cytokines has allowed a more precise definition of immunopathogenesis of leishmaniasis. Preliminary data from leishmaniasis patients lend support to this concept of altered immunomodulation. Furthermore, the data from leishmaniasis patients lend support to this concept of altered enhancement of therapeutic response by interferon-gamma has provided a new approach for treatment of patients using recombinant cytokines and for the study of the disease. Current research for early diagnosis, alternative therapies and need for vaccines are reviewed in the context of the immunopathology of leishmaniasis.

Pulmonary delivery of powders and solutions containing recombinant human granulocyte colony-stimulating factor (rhG-CSF) to the rabbit

Two powder formulations (MMAD < 4 microns) containing rhG-CSF were insufflated (IF) via an endotracheal tube at doses of 5, 75 or 500 micrograms/kg to New Zealand white rabbits. Doses of 5 and 500 micrograms/kg of solutions were administered by intratracheal instillation (IT), subcutaneous (SC) injection in the thigh and intravenous injection (i.v.) via the marginal ear vein. Blood samples were removed at regular intervals from an indwelling jugular catheter. Blood was analyzed directly for total white blood cell counts (WBC). Plasma was assayed for rhG-CSF by a specific ELISA. The distribution of radioactive dose in lung tissue was found after administering Tc99m HSA in solution or when incorporated into powders. The pharmacokinetics and pharmacodynamics were determined for all routes of administration. High dose IV concentration vs. time profiles declined biexponentially (t1/2 alpha = 0.6 +/- 0.2 hrs, t 1/2 beta = 4.6 +/- 0.2 hrs, n = 8). Clearance was does dependent (11.6 +/- 2.6 [500 micrograms/kg, n = 8] vs; 21.8 +/- 3.3 ml/hr/kg [5 micrograms/kg, n = 5]). A normal systemic response was obtained after IF, indicating that rhG-CSF retains activity in the solid state. Dissolution and absorption of rhG-CSF from the powders were not rate limiting. The plasma concentration vs. time profiles peaked at similar times to those after IT (Tmax 1-2 hrs) but were earlier than obtained after SC (Tmax 6-10 hrs). Powders were less efficiently dosed to the lung lobes after insufflation compared with instillates (14.7 +/- 10.5 vs. 60.1 +/- 10.6%), resulting in bioavailabilities ranging from 5 to 33%.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone marrow cell response following induction of acute inflammation in different strains of mice

The magnitude of the macrophage inflammatory response differs among inbred mouse strains. Mice of the A/J strain respond poorly to sterile inflammatory stimuli while those of the C57BL/6 strain show a strong response. Inflammatory macrophages found at the site of inflammation are the product of bone marrow (BM) myeloid stem cells. Mice of the A/J strain were found to have half the number of BM nucleated cells per femur than those of the C57BL/6 strain. The lower BM cellularity may be one reason for the poor macrophage inflammatory response observed in A/J mouse strain. Using A x B/B x A recombinant inbred mouse strains, we determined that the number of nucleated cells per femur found in normal mice was not a determining factor of the magnitude of the macrophage inflammatory response. One additional explanation for the poor macrophage inflammatory response in mice of the A/J strain is their deficiency in the C5 component of complement. Using a C5-sufficient A/J.C5 congenic strain, we have previously shown that the presence of C5 on the A/J background improved their inflammatory response. We compared A/J and A/J.C5 mouse strains to determine whether or not C5 had an impact on the BM cell response to inflammatory stimulus. The presence of C5 on the A/J background could contribute to the improvement of the inflammatory response in mice of the A/J.C5 strain by inducing a greater number of nucleated cells to exit the BM compartment early following induction of inflammation.

The magnitude of macrophage inflammatory response does not directly depend on ability of bone marrow cells to respond to interleukin-3 in mice of different strains

The multicolony stimulating factor Interleukin-3 (IL-3) has a role in regulating the proliferation, differentiation, and survival of myeloid stem cells and committed progenitor cells within each of the myeloid lineages. It has been referred to as an emergency factor appearing following triggering of an inflammatory response. The ability of bone marrow (BM) stem cells to respond to a stimulus such as IL-3 in vitro may reflect the in vivo capacity of BM stem cells to generate newly BM-derived macrophages being recruited to an inflammatory site. Both parameters, namely the BM cell response to in vitro IL-3 treatment and the magnitude of the macrophage inflammatory response vary among inbred mouse strains. Mice of the A/J strain are known to have weak macrophage inflammatory response to a phlogistic agent and their BM cells are hyporesponsive to IL-3 exposure. In contrast, mice of the C57BL/6 strain mount a high macrophage inflammatory reaction to a stimulus, and their BM cells strongly proliferate in response to the presence of IL-3. Thus, we examined whether or not the type of BM cell response to IL-3 (i.e., A/J- or C57BL/6-like) determines the magnitude of the macrophage inflammatory response using the A x B/B x A recombinant inbred (RI) mouse strain system. The two traits were found not to cosegregate, suggesting that they are not linked. The continuous strain distribution pattern of the magnitude of the macrophage inflammatory response obtained in mice of the A x B/B x A RI strains implies that this trait is under the control of several genes.

Comparative evaluation of the colony-stimulating factors induction potential of Plasmodium cynomolgi-infected monkey erythrocytes and soluble antigens

Plasmodium cynomolgi total antigens soluble in culture medium (P.c.SA), and noninfective P. cynomolgi-infected monkey erythrocytes (P.c.IE) were compared for their potential to induce colony-stimulating factors (CSFs). When injected intravenously in monkeys, both preparations induced an increase in the serum CSFs levels; P.c.IE appeared to be 1.6-fold more potent than the P.c.SA. In vitro P.c.IE induced 1.8-fold more CSF by monkey blood monocyte-derived macrophages than P.c. However, both in vivo and in vitro, the peak CSFs levels induced by P.c.SA were attained apparently 8 h earlier. CSF generated by P.c.SA and P.c.IE induced the formation of macrophage, granulocyte and granulocyte-macrophage colonies, in vitro; P.c.IE-generated CSF induced the formation of significantly (P < 0.01) higher numbers of granulocyte-macrophage colonies, indicating that the CSF induced by them stimulated different biological responses. The CSF induction appeared to be LPS-independent.

Enhanced mucosal cytokine production in inflammatory bowel disease

Proliferation, maturation, chemotaxis, and activation of neutrophils and monocytes are mediated largely by cytokines, including colony-stimulating factors and lymphokines. Cytokines produced in the intestinal mucosa contribute to the increased migration of neutrophils and monocytes into the lesion of inflammatory bowel disease and to the activation of these inflammatory cells. Lamina propria mononuclear cells isolated from colon tissue from 14 patients with inflammatory bowel disease (IBD) and from histologically normal controls were studied. Cells from IBD-affected tissue produced significantly more colony-stimulating factor activity (1402 +/- 252 U) per 2 x 10(6) cells than those from normal mucosa (362 +/- 85 U), mainly because of the increased production of granulocyte colony-stimulating factor and interleukin 1. This was accompanied by increases in the amount of specific messenger RNA for these two cytokines in lamina propria mononuclear cells from mucosa of patients with Crohn's disease (CD) compared with normal controls. By contrast, there was a substantial reduction in interleukin 3 production in CD and in ulcerative colitis lamina propria mononuclear cells, and this was reflected in significantly reduced expression of interleukin 3 messenger RNA in CD cells. Of the agents used in the therapy of IBD, hydrocortisone and 5-aminosalicylic acid, but not cyclosporin A, markedly suppressed in vitro production of cytokines by lamina propria mononuclear cells, suggesting that their therapeutic efficacy in vivo may be due in part to down-regulation of cytokine production in the inflamed mucosa.

Interleukins: biological properties and therapeutic potential

Interleukins are biologically active glycoproteins derived primarily from activated lymphocytes and macrophages. Tremendous insight into the biochemical and biological properties of interleukins has been gained with advances in recombinant DNA technology, protein purification, and cell-culture techniques. The biological properties of interleukins include induction of T-lymphocyte activation and proliferation, augmentation of neutrophil, macrophage, and T-lymphocyte cytotoxicity, and promotion of B lymphocyte and multilineage bone marrow stem-cell precursor growth and differentiation. Interleukins may play a role in the pathogenesis of several important diseases. Interleukin therapy is likely to play an important role in the treatment of cancer, infectious diseases, and immunodeficiency syndromes.

Cloning and sequencing of the ovine gamma-interferon gene

Cytokines are major modulators of the immune system of all animals. The cloning and expression of recombinant cytokine genes have permitted the analysis of their immune function and role in the control of the immune response to disease and vaccination. While human, murine, and bovine genes have been cloned and sequenced, the cloning of ovine cytokine genes has not yet been reported. As sheep are of dominant economic importance to the Australian farming industry, it is of significance to clone and express these genes to facilitate the development of new and better vaccines and pharmaceuticals. We have initially selected ovine gamma-interferon (gamma-IFN) as a target cytokine gene. By the use of the polymerase chain reaction (PCR), using primers based on the bovine gamma-interferon sequence, we have amplified the ovine gamma-interferon gene from crude messenger RNA extracted from lymphocytes. After cloning and DNA sequencing the gene, we found that ovine gamma-IFN is 93% identical to bovine gamma-IFN in amino acid sequence. This result indicates that the PCR method will be a rapid and efficient means for cloning other ovine cytokine genes.

Granulocyte-macrophage colony-stimulating factor augments neutrophil killing of Torulopsis glabrata and stimulates neutrophil respiratory burst and degranulation

The effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) on the interaction between the fungus Torulopsis glabrata and human neutrophils was examined. Pre-incubation of neutrophils with GM-CSF increased the neutrophil fungal killing. The cytokine also increased the oxygen-dependent respiratory burst in response to opsonized fungi, measured by the lucigenin-dependent chemiluminescence assay and superoxide release. Under the same conditions the cytokine augmented release of constituents from both specific and azurophilic granules. Besides these priming effects, GM-CSF was a weak stimulus of the neutrophil respiratory burst and degranulation. The priming and stimulatory effects of GM-CSF were observed at 10-1000 U/ml with an optimal concentration of 100 U/ml.

Cloning and sequencing of the cDNA for ovine granulocyte-macrophage colony-stimulating factor (GM-CSF)

Colony-stimulating factors (CSFs) are not only regulators of haemopoiesis but can also enhance the function of mature myeloid cells, and are therefore potential immune adjuvants. By use of the polymerase chain reaction (PCR) with primers based on the bovine granulocyte-macrophage CSF (GM-CSF) sequence, we have amplified the cDNA for ovine GM-CSF, produced from crude mRNA extracted from alveolar macrophages. The PCR product was cloned into pUC119, and electroporated into Escherichia coli. The complete nucleotide sequence of two clones, and the partial sequence of eight others, was determined. At the nucleotide and amino acid levels, the ovine and bovine GM-CSF sequences are 91% and 81% homologous, respectively.

Expression of granulocyte and granulocyte-macrophage colony-stimulating factors by human non-hematopoietic tumor cells

The expression of granulocyte colony-stimulating factor (G-CSF) mRNA was studied in human non-hematopoietic tumors, including 18 cases of lung cancers 10 cases of stomach cancers, three cases of glioblastomas, and one case each of breast phyllode sarcoma, thyroid cancer, and hepatocellular carcinoma. Northern blot analysis detected G-CSF mRNA in two of the lung cancer cases, in one of the glioblastoma cases, and in both the breast phyllode sarcoma and hepatocellular carcinoma cases. Since G-CSF receptors were not detected on the tumor cells by 125I-G-CSF binding assay, G-CSF autocrine loop are probably not involved in the growth of these G-CSF-producing tumors. Interestingly, granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA was concomitantly expressed in most of these G-CSF-producing tumors. No major gene deletions or rearrangements of G-CSF and GM-CSF genes were demonstrated by Southern blot analysis in the tumors expressing G-CSF and GM-CSF mRNAs except for one of the glioblastomas (G3) in which one chromosome 17 allele was deleted. Although the mechanism of the concomitant expression of G-CSF and GM-CSF mRNA is unknown, relatively high frequency of this phenomenon suggests the presence of common transcriptional factors acting on regulatory regions of G-CSF and GM-CSF genomes.

Haemopoietic growth factors

Erythropoietin, GM-colony-stimulating factor and G-colony-stimulating factor are the first recombinant haemopoietic growth factors to reach clinical use. There are a number of additional haemopoietic regulators that have now been cloned and are being mass-produced with a view to clinical use. The next decade should witness exciting advances in the clinical treatment of haematological diseases and infections that will be comparable with those that were seen last with the introduction of effective treatments for pernicious anaemia.

Induction of inflammatory responses by endotoxin in the non-lactating ovine mammary gland

In non-lactating ewes, intramammary infusion of endotoxin provokes an intense but transient inflammatory response as assessed by mammary lavage. The variability of the method for sampling the leucocytes in mammary secretions was examined. Initial lavage with 20 ml pyrogen-free saline recovered 83.0 +/- 2.8 and 84.4 +/- 3.0% of the total leucocyte numbers harvested by three serial washes of quiescent and inflamed glands, respectively. Lavage of glands prior to infusion of endotoxin did not affect the magnitude of the subsequent inflammatory response. Three treatments at 3.5 day intervals with the glucocorticoid, dexamethasone, which inhibits the inflammatory response to intramammary infusion of antigen in systemically immunized ewes, did not affect the inflammatory response to endotoxin. However, the variability of the inflammatory response to activated complement was greatly increased in dexamethasone-treated ewes; this effect was attributed to the induction of lactation which results in loss of sensitivity of the gland to the inflammatory activity of activated complement. The results indicated that the macrophages and lymphocytes which are present in mammary secretions in large numbers, and dexamethasone-sensitive lymphocytes in the gland, played a trivial role in the induction of inflammatory responses to endotoxin.