Properties of isolated red pulp macrophages from mouse spleen

Malaria Elimination in Africa: Rethinking Strategies for Plasmodium vivax and Lessons from Botswana

The global malaria community has picked up the theme of malaria elimination in more than 90% of the world's population in the next decade. Recent reports of Plasmodium vivax (P. vivax) in sub-Saharan Africa, including in Duffy-negative individuals, threaten the efforts aimed at achieving elimination. This is not only in view of strategies that are tailored only to P. falciparum elimination but also due to currently revealed biological characteristics of P. vivax concerning the relapse patterns of hypnozoites and conservation of large biomasses in cryptic sites in the bone marrow and spleen. A typical scenario was observed in Botswana between 2008 and 2018, which palpably projects how P. vivax could endanger malaria elimination efforts where the two parasites co-exist. The need for the global malaria community, national malaria programs (NMPs), funding agencies and relevant stakeholders to engage in a forum to discuss and recommend clear pathways for elimination of malaria, including P. vivax, in sub-Saharan Africa is warranted.

Pre-existing anti-polyethylene glycol antibody reduces the therapeutic efficacy and pharmacokinetics of PEGylated liposomes

Rationale: Increasing frequency of human exposure to PEG-related products means that healthy people are likely to have pre-existing anti-PEG antibodies (pre-αPEG Ab). However, the influence of pre-αPEG Abs on the pharmacokinetics (PK) and therapeutic efficacy of LipoDox is unknown.

Methods: We generated two pre-αPEG Ab mouse models. First, naïve mice were immunized with PEGylated protein to generate an endogenous αPEG Ab titer (endo αPEG). Second, monoclonal αPEG Abs were passively transferred (αPEG-PT) into naïve mice to establish a αPEG titer. The naïve, endo αPEG and αPEG-PT mice were intravenously injected with ¹¹¹in-labeled LipoDox to evaluate its PK. Tumor-bearing naïve, endo αPEG and αPEG-PT mice were intravenously injected with ¹¹¹in-labeled LipoDox to evaluate its biodistribution. The therapeutic efficacy of LipoDox was estimated in the tumor-bearing mice.

Results: The areas under the curve (AUC)_last of LipoDox in endo αPEG and αPEG-PT mice were 11.5- and 15.6- fold less, respectively, than that of the naïve group. The biodistribution results suggested that pre-αPEG Ab can significantly reduce tumor accumulation and accelerate blood clearance of ¹¹¹In-labeled LipoDox from the spleen. The tumor volumes of the tumor-bearing endo αPEG and αPEG-PT mice after treatment with LipoDox were significantly increased as compared with that of the tumor-bearing naïve mice.

Conclusions: Pre-αPEG Abs were found to dramatically alter the PK and reduce the tumor accumulation and therapeutic efficacy of LipoDox. Pre-αPEG may have potential as a marker to aid development of personalized therapy using LipoDox and achieve optimal therapeutic efficacy.

Postburn monocytes are the major producers of TNF-alpha in the heterogeneous splenic macrophage population

Increased tumor necrosis factor (TNF)-alpha production by postburn splenic macrophages is well documented. Splenic macrophages are a heterogeneous population, and the effect of thermal injury on these subpopulations has not been documented. We examined the effects of scald injury on myeloid cells with the phenotype of red pulp, white pulp, and marginal zone monocyte/macrophages. We found that thermal injury greatly increased the number of splenocytes with the phenotype of white pulp monocytes. These cells were the major producers of TNF-alpha in the postburn spleen. Cells with the red pulp macrophage phenotype had an increased ability to make TNF-alpha after burn injury, but had only half the capacity to make TNF-alpha as did postburn monocytes. The postburn changes in TNF-alpha production correlated with an increased in vivo susceptibility to endotoxin. The increase in monocytes in the spleen from postburn days 1 to 10 correlated with an increasing ability of splenocytes to produce granulocyte colony-stimulating factor, monocyte chemoattractant protein 1, macrophage inflammatory protein 2, and macrophage inflammatory protein 1-alpha. These data suggest that the monocyte is a major source of inflammatory cytokines in the postburn spleen.

Isolation, purification and flow cytometric analysis of human intrahepatic lymphocytes using an improved technique

Intrahepatic lymphocytes (IHL) with their diverse and distinctive subsets emphasise the importance of the liver as a site of immunological activity, but special care is required for their isolation and characterisation. Protocols for IHL isolation, purification and FACS analysis were devised and compared with published extraction protocols. We have reduced the time that IHL are exposed to potentially damaging enzymes during extraction and purified specific subsets using monoclonal antibody (mAb)-coated magnetic microbeads. This has yielded IHL populations with higher viability than previously described protocols (92-95%, compared with 39-86%). Flow cytometric characterisation of IHL subset immunophenotypes was optimised by combining CD45 staining (fluorescence gating) with traditional light scatter properties. Using a panel of mAb and liver biopsies obtained from 23 cadaveric liver transplant donors, we show that the normal liver contains a heterogeneous IHL population with distinctive phenotypes. CD8+ IHL was the predominant population with a mean CD4/CD8 ratio of 1:1.7. Up to 40% of IHL expressed gammadeltaTCR and a third expressed CD56 NK marker; indicating a site of intense immunological activity. The techniques described will allow these cell types to be isolated, fully characterised and their physiological functions to be determined. The histologically normal liver contains heterogeneous and diverse IHL with large numbers of CD8+, NK, NKT and gammadelta+ cells.

The IFN-inducible Golgi- and endoplasmic reticulum- associated 47-kDa GTPase IIGP is transiently expressed during listeriosis

Members of the 47-kDa GTPase family are implicated in an IFN-gamma-induced, as yet unclear, mechanism that confers innate resistance against infection with intracellular pathogens. Overt immunological parameters are apparently uncompromised in mice deficient for individual members and the prototype of this family, IGTP, localizes to the endoplasmic reticulum. This suggests that these GTPases are involved in intracellular defense. We analyzed the expression of the 47-kDa GTPase cognate, IIGP, in splenic sections from mice infected with the intracellular pathogen Listeria monocytogenes by immunohistochemistry. An early transient IIGP induction was observed revealing the IFN-gamma responsiveness of cellular subcompartments within the spleen in early listeriosis. Marginal metallophilic macrophages and endothelial cells within the red and white pulp strongly expressed IIGP, while other splenocytes remained negative. In vitro analyses show that both type I and type II IFNs are prime stimuli for IIGP induction in various cells, including L. monocytogenes-infected or LPS-stimulated macrophages, endothelial cells, and activated T cells. Contrary to the subcellular localization of IGTP, IIGP was predominantly associated with the Golgi apparatus and also localizes to the endoplasmic reticulum. We conclude that IIGP exerts a distinct role in IFN-induced intracellular membrane trafficking or processing.

Role of eicosanoids in regulation of macrophage phagocytic functions by platelet-activating factor during endotoxic shock

We studied the role of eicosanoids in the regulation of macrophage phagocytic functions by products secreted in heterogeneous populations of macrophages and platelet-activating factor during endotoxic shock. Phagocytic activity depended on the metabolism of arachidonic acid in target macrophages and the ratio between its cyclooxygenase and lipoxygenase metabolites produced by heterogeneous populations of macrophages and affecting target cells. The regulatory effect of platelet-activating factor on phagocytosis was related to its interaction with products of the arachidonic acid cascade. Depending on the quantitative ratio of eicosanoids, platelet-activating factor produced various effects on phagocytic functions of heterogeneous macrophage populations.

The role of the spleen, especially regarding changes in both thromboxane A2 and the remnant liver dysfunction after extensive hepatectomy

The plasma levels of thromboxane B2 (TxB2) and 6-keto-prostaglandin F1alpha (6-KF) in the peripheral and portal blood increase after an extensive hepatectomy, and even more so in cases with complications. In this cell biological study, we estimated the prostanoids in the portal system to clarify which organ produces them, while also evaluating the effect of a splenectomy in conjunction with an extensive hepatectomy. Our results showed that the level of TxB2 in the splenic vein was significantly higher than that in the mesenteric vein. Furthermore, the TxA2 produced by splenic macrophages after an extensive hepatectomy was significantly more than after a sham operation. We also observed the hepatocyte damage to be less in the group that underwent an 84% hepatectomy and splenectomy than in the group that underwent the same hepatectomy without a splenectomy. It therefore appears important both to suppress the splenic macrophages from producing TxA2 and to prevent remnant hepatic dysfunction after an extensive hepatectomy.

Nitric oxide synthase expression in macrophages of Histoplasma capsulatum-infected mice is associated with splenocyte apoptosis and unresponsiveness

Splenic macrophages from Histoplasma capsulatum-infected mice express inducible nitric oxide synthase (iNOS), and the iNOS expression correlates with severity of the infection. We examined whether production of NO is responsible for apoptosis and the anti-lymphoproliferative response of splenocytes from mice infected with H. capsulatum. In situ terminal deoxynucleotidyl transferase nick end labeling revealed apoptotic nuclei in cryosections of spleen from infected but not normal mice. Splenocytes of infected mice were unresponsive to stimulation by either concanavalin A or heat-killed H. capsulatum yeast cells. Splenocyte responsiveness was restored by addition to the medium of NG-monomethyl-L-arginine, a known inhibitor of NO production. The proliferative response of splenocytes from infected mice was also restored by depletion of macrophages or by replacement with macrophages from normal mice. In addition, expression of iNOS returned to its basal level when the animals had recovered from infection. These results suggest that suppressor cell activity of macrophages is associated with production of NO, which also appears to be an effector molecule for apoptosis of cultured splenocytes from infected mice.

Antihistoplasma effect of activated mouse splenic macrophages involves production of reactive nitrogen intermediates

The mechanism by which recombinant murine gamma interferon (rMuIFN-gamma) and bacterial lipopolysaccharide (LPS) activate mouse resident splenic macrophages to inhibit the intracellular growth of the fungus Histoplasma capsulatum was examined. Growth inhibition depended on L-arginine metabolism. The growth inhibitory state normally induced by rMuIFN-gamma and LPS in resident splenic macrophages did not occur when the macrophages were cultured in the presence of NG-monomethyl-L-arginine, a competitive inhibitor of L-arginine metabolism. Resident splenic macrophages treated with rMuIFN-gamma and LPS produced nitrite (NO2-), an end product of L-arginine metabolism. When macrophages were cultured in the presence of NG-monomethyl-L-arginine together with rMuIFN-gamma and LPS, only baseline levels of NO2- were detected. Spleen cells from H. capsulatum-infected mice produced high levels of NO2- in culture. The production of NO2- correlated with in vitro inhibition of the intracellular growth of H. capsulatum. Anti-tumor necrosis factor alpha antibody did not block NO2- production by the immigrant splenic macrophages and did not abolish the antihistoplasma activity.

Zanvil Alexander Cohn 1926-1993

Zanvil Alexander Cohn, an editor of this Journal since 1973, died suddenly on June 28, 1993. Cohn is best known as the father of the current era of macrophage biology. Many of his scientific accomplishments are recounted here, beginning with seminal studies on the granules of phagocytes that were performed with his close colleague and former editor of this Journal, James Hirsch. Cohn and Hirsch identified the granules as lysosomes that discharged their contents of digestive enzymes into vacuoles containing phagocytosed microbes. These findings were part of the formative era of cell biology and initiated the modern study of endocytosis and cell-mediated resistance to infection. Cohn further explored the endocytic apparatus in pioneering studies of the mouse peritoneal macrophage in culture. He described vesicular inputs from the cell surface and Golgi apparatus and documented the thoroughness of substrate digestion within lysosomal vacuoles that would only permit the egress of monosaccharides and amino acids. These discoveries created a vigorous environment for graduate students, postdoctoral fellows, and junior and visiting faculty. Some of the major findings that emerged from Cohn's collaborations included the radioiodination of the plasma membrane for studies of composition and turnover; membrane recycling during endocytosis; the origin of the mononuclear phagocyte system in situ; the discovery of the dendritic cell system of antigen-presenting cells; the macrophage as a secretory cell, including the release of proteases and large amounts of prostaglandins and leukotrienes; several defined parameters of macrophage activation, especially the ability of T cell-derived lymphokines to enhance killing of tumor cells and intracellular protozoa; the granule discharge mechanism whereby cytotoxic lymphocytes release the pore-forming protein perforin; the signaling of macrophages via myristoylated substrates of protein kinase C; and a tissue culture model in which monocytes emigrate across tight endothelial junctions. In 1983, Cohn turned to a long-standing goal of exploring host resistance directly in humans. He studied leprosy, focusing on the disease site, the parasitized macrophages of the skin. He injected recombinant lymphokines into the skin and found that these molecules elicited several cell-mediated responses. Seeing this potential to enhance host defense in patients, Cohn was extending his clinical studies to AIDS and tuberculosis. Zanvil Cohn was a consummate physician-scientist who nurtured the relationship between cell biology and infectious disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Gamma interferon cooperates with lipopolysaccharide to activate mouse splenic macrophages to an antihistoplasma state

Inhibition of the intracellular growth of Histoplasma capsulatum by murine resident red pulp splenic macrophages was examined. Splenic macrophages, unlike resident peritoneal macrophages, required a prolonged preincubation (18 h) with recombinant murine gamma interferon (rMuIFN-gamma) for activation. To be fully activated, the splenic macrophages required incubation with rMuIFN-gamma in combination with 0.1 microgram of lipopolysaccharide (LPS) per ml. Splenic macrophages stimulated with rMuIFN-gamma, LPS, or rMuIFN-gamma and LPS produced tumor necrosis factor alpha (TNF-alpha), but recombinant murine TNF-alpha (rMuTNF-alpha) did not activate macrophages when used alone or as a second signal with rMuIFN-gamma. Anti-TNF-alpha antibody did not block IFN-gamma-LPS activation of splenic macrophages to any significant extent. One hundred micromolar ferrous sulfate antagonized IFN-gamma-LPS activation of splenic macrophages, indicating that iron was involved in the fungistatic activity of cytokine-stimulated phagocytes. Our results indicate that (i) splenic macrophages differ significantly from peritoneal macrophages in their requirements for activation and (ii) the mechanism by which splenic macrophages exert their antifungal effects involves iron.

Early activation of splenic macrophages by tumor necrosis factor alpha is important in determining the outcome of experimental histoplasmosis in mice

Experimental infection of animals with Histoplasma capsulatum caused a massive macrophage infiltration into the spleen and induced the production of tumor necrosis factor alpha (TNF-alpha) locally. The cytokine was also produced in vitro by peritoneal exudate macrophages exposed to a large inoculum of yeast cells. Depletion of the cytokine by injection of polyclonal sheep anti-TNF-alpha antibody was detrimental to sublethally infected mice. Fungous burdens in the spleens of TNF-alpha-depleted mice were higher than they were in the infected control mice at days 2, 7, and 9 after infection, and the antibody-treated animals succumbed to the infection. Histopathological study of spleen sections revealed that splenic macrophages were not able to control proliferation of intracellular yeasts as a result of TNF-alpha depletion. It seems that TNF-alpha plays a role in early activation of splenic macrophages which is important in controlling the outcome of an infection.

Leprosy and cell-mediated immunity

The intradermal injection of the purified protein derivative of tuberculin into lepromatous leprosy patients leads to a local cell-mediated immune response and to the extensive destruction of Mycobacterium leprae. This local response also occurs after intradermal injection of recombinant human interleukin-2; when administered over an 8-day period interleukin-2 evokes a systemic cell-mediated immune response and a reduction in the bacillary burden.

Characterization and expression of the antigen present on resident rat macrophages recognized by monoclonal antibody ED2

Because of the absence of a specific marker for labeling resident macrophages in the rat, there is almost no information available regarding the properties of individual resident macrophages in different organs. The recently described and in our laboratory developed mAb ED2, has been shown to exclusively recognize resident macrophages. The present study examines expression, function and structure of the ED2 antigen to obtain more information about the marker and therefore, more information about resident macrophages. In earlier studies, the expression of ED2 could not be induced by a range of macrophage stimulating factors under non-adherent culture conditions. We show a highly inducible expression of the ED2 antigen under adhering, non proliferating conditions as well as in long-term bone marrow cultures. ED2 appears to recognize a surface protein on resident macrophages consisting of three protein chains of 175, 160, and 95 kDa.

Isolation and flow cytometric analysis of the free lymphomyeloid cells present in murine liver

Recruitment of circulating lymphomyeloid cells in the liver during infection often plays a critical role, mediating control or exacerbation of the pathogen growth. This paper describes a simple and rapid technique to recover these lymphomyeloid cells from a normal or an infected liver. After portal perfusion with saline buffer, the liver is gently dissociated on steel screens and the resulting cell population spun in 35% Percoll in 100 IU/ml Calciparine to remove all nuclei and cell debris: the recovery of a pure liver lymphomyeloid cell population is usually achieved in 40-60 min. Phenotypic and functional analysis could then be easily carried out on this cell population. This methodology was applied to normal mouse liver: flow cytometric analysis of the purified free lymphomyeloid cells showed the presence of T lymphocytes (46% +/- 3 with a CD4/CD8 ratio of 2.8), B lymphocytes (20% +/- 2 IgG and 30% IgM positive) and myelomonocytic cells (14% +/- 2 complement receptor type III positive).

Immunological and nonimmunological control of severity of Trypanosoma musculi infections in C3H and C57BL/6 inbred mice

Studies concerned with the mechanisms responsible for relative resistance or susceptibility of strains of inbred mice to Trypanosoma musculi infections are presented. Treatment with 400 rads of ionizing radiation, silica dust, or trypan blue (reticuloendothelial blocking agents) rendered C3H mice unable to control the initial maximum level of parasite growth, and the mice died of overwhelming infections. In contrast, similarly treated C57BL/6 (relatively resistant) mice controlled initial trypanosome growth as well as controls; however, the duration of infection, preceding eventual cure, was approximately doubled. Combined treatment with trypan blue and 400 rads of radiation resulted in much higher initial levels of infection in C57BL/6 mice, and about half of the mice died; the remaining mice eventually recovered after a prolonged course of infection. These results indicate that a nonimmunological mechanism, which controls initial infection, and an immunological mechanism cooperate to limit T. musculi infections in normal mice. We present results that suggest that both mechanisms are less effective in C3H than in C57BL/6 mice. The initial control of infection presumably reflects the activity of some type(s) of phagocytic effector cell; we show, however, that the initial control of infection is not an attribute of the liver Kupffer cells. Identification and characterization of the cells capable of controlling initial infection could lead to procedures for enhancing their function and, thus, to enhanced resistance to, and elimination of, trypanosome infections.

Mouse macrophage hemagglutinin (sheep erythrocyte receptor) with specificity for sialylated glycoconjugates characterized by a monoclonal antibody

An inhibitory rat mAb, SER-4, has been raised to the mouse macrophage (M phi)-restricted hemagglutinin, sheep erythrocyte receptor (SER), which binds unopsonized sheep erythrocytes through recognition of sialylated glycoconjugates. This receptor was originally defined on mouse resident bone marrow M phi where it was implicated in adhesive interactions of these cells with proliferating hematopoietic cells. In the present study using mouse serum-induced thioglycollate-elicited peritoneal M phi (TPM) as a model system for SER expression, mAb SER-4 IgG2a completely blocked rosette formation at 1 microgram/ml. The inhibition was likely to be via steric hindrance rather than through a direct interaction with the putative sialic acid binding site of SER because F(ab')2 and Fab fragments of mAb SER-4 gave a maximum inhibition of 50-60% and 0% respectively, despite binding effectively to the SER-4 antigen (Ag). Immunoprecipitation and Western blotting experiments with cultured M phi or tissue extracts demonstrated that the Ag recognized by SER-4 mAb is a single chain molecule with an apparent Mr by SDS-PAGE of 185 x 10(3) (reduced) or 170 x 10(3) (non-reduced) and is distinct from members of the leukocyte common Ag family. Expression of SER and SER-4 Ag in culture were closely correlated and depended on the presence of mouse serum for optimal induction. Further evidence that the SER-4 Ag is functionally equivalent to SER was provided by immunocytochemistry in which the overall pattern of staining in tissues was consistent with previous rosetting experiments. In the bone marrow, expression of the SER-4 Ag was restricted to the resident bone marrow M phi population with no expression on monocytes. High expression was also observed on stromal M phi within the subcapsular sinus and medullary cords in lymph nodes and on marginal metallophils in the spleen. These results therefore confirm that SER is a novel M phi-restricted receptor whose distribution and properties indicate a role in cellular interactions in hematopoietic and lymphoid tissues.

The reconstitution of cell-mediated immunity in the cutaneous lesions of lepromatous leprosy by recombinant interleukin 2

Human rIL-2 (10-30 micrograms) was injected intradermally into the skin of patients with lepromatous leprosy with high bacillary loads. All patients responded to the lymphokine with local areas of induration that peaked at 24 h and persisted for 4-7 d irrespective of whether the site was "normal skin" or a nodular lesion. Within 24 h there was an extensive emigration of T cells and monocytes into the site. The percentage of the dermis infiltrated by mononuclear cells increased by more than sevenfold, peaking at 4 d and persisting for greater than 15 d. Both CD4+ and CD8+ T cells entered the site. T cells of CD4+ phenotype predominated at 2-7 d but by 11 d, CD8+ cells were predominant. Considerable numbers of T6+ Langerhans' cells appeared in the dermis by 72 h and persisted for 3 wk. By 4 d the thickness of the overlying epidermis had increased twofold, and keratinocytes were expressing MHC class II antigen and the IFN-gamma-induced peptide IP-10. Starting at 48 h, there was an extensive destruction of mononuclear phagocytes that contained structurally intact or fragmented M. leprae observed at the electron microscope level. The organisms, either free or contained within endocytic vacuoles, were discharged into the extracellular space and then reingested by blood-borne monocytes. This was followed by marked reductions in the number of acid-fast organisms in the injected site, evident as early as 4-7 d and more marked at 2-3 wk after injection. 13 of 15 patients exhibited a disposal of acid-fast bacilli ranging from 5- to 1,000-fold with a mean value of approximately 100-fold. The administration of IL-2 leads to the generation of an effective cell-mediated immune response, recapitulating an antigen-driven event and leading to striking local reductions in M. leprae. In comparison with the purified protein derivative of tuberculin reaction, bacilli are cleared more promptly, although emigratory cells persist for a shorter time.