The Osler slide, a demonstration of phagocytosis from 1876

High spatial resolution imaging of subcellular macro and trace element distribution during phagocytosis

The bioavailability of trace elements in the course of evolution had an essential influence on the emergence of life itself. This is reflected in the co-evolution between eukaryotes and prokaryotes. In this study, the influence and cellular distribution of bioelements during phagocytosis at the host-pathogen interface was investigated using high-resolution nanoscale secondary ion mass spectrometry (NanoSIMS) and quantitative inductively coupled plasma mass spectrometry (ICP-MS). In the eukaryotic murine macrophages (RAW 264.7 cell line), the cellular Fe / Zn ratio was found to be balanced, whereas the dominance of iron in the prokaryotic cells of the pathogen Salmonella enterica Serovar Enteritidis was about 90% compared to zinc. This confirms the evolutionary increased zinc requirement of the eukaryotic animal cell. Using NanoSIMS, the Cs+ primary ion source allowed high spatial resolution mapping of cell morphology down to subcellular level. At a comparable resolution, several low abundant trace elements could be mapped during phagocytosis with a RF plasma O- primary ion source. An enrichment of copper and nickel could be detected in the prokaryotic cells. Surprisingly, an accumulation of cobalt in the area of nuclear envelope was observed indicating an interesting but still unknown distribution of this trace element in murine macrophages.

How Phagocytes Acquired the Capability of Hunting and Removing Pathogens From a Human Body: Lessons Learned From Chemotaxis and Phagocytosis of Dictyostelium discoideum (Review)

How phagocytes find invading microorganisms and eliminate pathogenic ones from human bodies is a fundamental question in the study of infectious diseases. About 2.5 billion years ago, eukaryotic unicellular organisms-protozoans-appeared and started to interact with various bacteria. Less than 1 billion years ago, multicellular animals-metazoans-appeared and acquired the ability to distinguish self from non-self and to remove harmful organisms from their bodies. Since then, animals have developed innate immunity in which specialized white-blood cells phagocytes- patrol the body to kill pathogenic bacteria. The social amoebae Dictyostelium discoideum are prototypical phagocytes that chase various bacteria via chemotaxis and consume them as food via phagocytosis. Studies of this genetically amendable organism have revealed evolutionarily conserved mechanisms underlying chemotaxis and phagocytosis and shed light on studies of phagocytes in mammals. In this review, we briefly summarize important studies that contribute to our current understanding of how phagocytes effectively find and kill pathogens via chemotaxis and phagocytosis.

Differential Modulation of 25-hydroxycholecalciferol on Innate Immunity of Broiler Breeder Hens

Simple Summary

No predominant changes between R- vs. Ad-feed intake on leukocyte defense against pathogens were observed in broiler breeder hens despite some differences in inflammatory and respiratory burst responses. Overall, supplemental 25-OH-D₃ had more pronounced effects on the innate immunity of Ad-hens. In vitro studies confirmed the differential effects of 25-OH-D₃ to rescue immune functions altered by glucose and/or palmitic acid exposure.

Abstract

Past immunological studies in broilers focused on juveniles within the rapid pre-slaughter growth period and may not reflect adult immune responses, particularly in breeders managed with chronic feed restriction (R). The study aimed to assess innate immune cell functions in respect to R vs. ad libitum (Ad) feed intake in breeder hens with and without dietary 25-hydroxycholecalciferol (25-OH-D₃) supplementation. Ad-feed intake consistently suppressed IL-1β secretion, respiratory burst, and cell livability in peripheral heterophils and/or monocytes along the feeding trial from the age of 51 to 68 weeks. Supplemental 25-OH-D₃ repressed IL-1β secretion and respiratory burst of both cells mostly in R-hens, but promoted monocyte phagocytosis, chemotaxis, and bacterial killing activity in Ad-hens in accompany with relieved hyperglycemia, hyperlipidemia, and systemic inflammation. Overnight cultures with leukocytes from R-hens confirmed the differential effects of 25-OH-D₃ to rescue immune functions altered by glucose and/or palmitic acid exposure. Studies with specific inhibitors further manifested the operative mechanisms via glucolipotoxicity in a cell type- and function-dependent manner. The results concluded no predominant changes between R- vs. Ad-feed intake on leukocyte defense against pathogens despite some differential differences, but supplemental 25-OH-D₃ exerts more pronounced effects in Ad-hens.

Digital Gene Expression Analysis of Epithelioid and Sarcomatoid Mesothelioma Reveals Differences in Immunogenicity

Malignant pleural mesothelioma (MPM) is an aggressive malignancy associated with asbestos exposure. Median survival ranges from 14 to 20 months after initial diagnosis. As of November 2020, the FDA approved a combination of immune checkpoint inhibitors after promising intermediate results. Nonetheless, responses remain unsatisfying. Adequate patient stratification to improve response rates is still lacking. This retrospective study analyzed formalin fixed paraffin embedded specimens from a cohort of 22 MPM. Twelve of those samples showed sarcomatoid, ten epithelioid differentiation. Complete follow-up, including radiological assessment of response by modRECIST and time to death, was available with reported deaths of all patients. RNA of all samples was isolated and subjected to digital gene expression pattern analysis. Our study revealed a notable difference between epithelioid and sarcomatoid mesothelioma, showing differential gene expression for 304/698 expressed genes. Whereas antigen processing and presentation to resident cytotoxic T cells as well as phagocytosis is highly affected in sarcomatoid mesothelioma, cell-cell interaction via cytokines seems to be of greater importance in epithelioid cases. Our work reveals the specific role of the immune system within the different histologic subtypes of MPM, providing a more detailed background of their immunogenic potential. This is of great interest regarding therapeutic strategies including immunotherapy in mesothelioma.

William Osler and the "fixed period" of creativity

In 1905, William Osler was the pre-eminent physician in American medical circles but was unknown to the general public. The latter suddenly learned of him through damning newspaper accounts of his address announcing his retirement from the Johns Hopkins Medical School. In it Osler mentioned two "fixed ideas" he held-(1) that most major advances in civilization have been made by men under age 40 (the "fixed period") and (2) that those over 60 should retire because they create little of significance and sometimes stifled the initiatives of younger colleagues. He highlighted the second idea with a Victorian novel describing a mythical society which chloroformed men at age 60. He never imagined that this literary allusion would be taken as a serious solution for his second idea. However, countless newspaper articles ridiculed the first and condemned him for the second. Scurrilous press attacks on him continued for several months and resurfaced occasionally thereafter. The extent of the public approbation can also be found in poems and stories linking him with euthanasia. Also discussed here are the sources of Osler's equanimity in the face of such public derision and the inner drives which accounted for over 1300 publications by him-nearly half of which were composed after age 40.

A brief historical and evolutionary perspective on the origin of cellular microbiology research

Integrated with both a historical perspective and an evolutionary angle, this opinion article presents a brief and personal view of the emergence of cellular microbiology research. From the very first observations of phagocytosis by Goeze in 1777 to the exhaustive analysis of the cellular defence mechanisms performed in modern laboratories, the studies by cell biologists and microbiologists have converged into an integrative research field distinct from, but fully coupled to immunity: cellular microbiology. In addition, this brief article is thought as a humble patchwork of the motivations that have guided the research in my group over a quarter century.

Photo-responsive liposomes composed of spiropyran-containing triazole-phosphatidylcholine: investigation of merocyanine-stacking effects on liposome-fiber assembly-transition

A spiropyran-containing triazole-phosphatidylcholine (SPTPC) was synthesized through a copper-catalyzed azide alkyne cyclo-addition (CuAAC) reaction. In water, SPTPCs self-assembled and a spontaneous spiropyran-to-merocyanine (SP-to-MC) isomerization occurred, resulting in coexistence of liposomes and fibers, and switching from the spiropyran (SP) to the merocyanine (MC) isomeric structure induced a reversible transition between these molecular assemblies. Study of the self-assembly of SPTPCs and photo-induced liposome-fiber assembly-transition revealed that the presence of MC enabled additional inter-membrane interaction during self-assembly and that the MC-stacking effect was the driving force for the assembly-transition. Exposure to UV light induced switching from SP to MC, where the planar structure of MC and the confinement of MC led to enhanced MC-stacking. The effect of MC-stacking was both advantageous and disadvantageous: MC-stacking perturbed the hydrophobic phase in the bilayer membrane and facilitated the liposome-to-fiber transition, otherwise the MC-stacking retarded switching of MC to SP, and caused an incomplete recovery of MC to SP during fiber-to-liposome recovery, thus a fatigue of SP was induced by MC-stacking during the liposome-to-fiber transition cycle. To decrease the intermolecular interactions and suppress MC-stacking, photo-inert triazole-phosphatidylcholine (TPC) was incorporated to prepare two-component TPC/SPTPC-liposomes, which exhibited better recovery kinetics. The photo-adaptive behavior of TPC/SPTPC-liposomes confirmed the disturbance of bilayer membranes by inter-membrane MC-stacking and the formation of MCTPC-enriched phases in the bilayer membrane.

Vitamin D both facilitates and attenuates the cellular response to lipopolysaccharide

Vitamin D has a range of non-skeletal health effects and has been implicated in the response to respiratory infections. The aim of this study was to assess the effect of vitamin D on the response of epithelial cells, neutrophils and macrophages to lipopolysaccharide (LPS) stimulation. BEAS-2B cells (airway epithelial cell line) and primary neutrophils and macrophages isolated from blood samples were cultured and exposed to LPS with and without vitamin D (1,25(OH)₂D). The production of IL-6, IL-8, IL-1β and TNF-α of all cells and the phagocytic capacity of neutrophils and macrophages to E. coli were assessed. Vitamin D had no effect on BEAS-2B cells but enhanced the production of IL-8 in neutrophils (p = 0.007) and IL-1β in macrophages (p = 0.007) in response to LPS. Both vitamin D (p = 0.019) and LPS (p < 0.001) reduced the phagocytic capacity of macrophages. These data suggest that the impact of vitamin D on responses to infection are complex and that the net effect will depend on the cells that respond, the key response that is necessary for resolution of infection (cytokine production or phagocytosis) and whether there is pre-existing inflammation.

A stratified myeloid system, the challenge of understanding macrophage diversity

The present issue of 'Seminars in Immunology' addresses the topic of macrophage biology, 100 years after the death of Elie Metchnikoff (May 1845-July 1916). As foreseen by Metchnikoff, the roles of macrophages in the maintenance of homeostasis and immunity against pathogens have become a broad and active area of investigation. We now start to realize that the myeloid system includes a multiplicity of cell types with diverse developmental origins and functions. Therefore, the textbook picture of a plastic and multifunctional macrophage does not meet the requirements of our current knowledge anymore. Further development toward a quantitative and molecular understanding of myeloid cell biology in vivo and their roles in tissue homeostasis and remodeling will benefit from taking this complexity into account. A tentative model to help in this pursuit and account for myeloid cell and macrophage diversity is discussed below.

The role of macrophages in the innate immune response to Streptococcus pneumoniae and Staphylococcus aureus: mechanisms and contrasts

Macrophages are critical mediators of innate immune responses against bacteria. The Gram-positive bacteria Streptococcus pneumoniae and Staphylococcus aureus express a range of virulence factors, which challenge macrophages' immune competence. We review how macrophages respond to this challenge. Macrophages employ a range of strategies to phagocytose and kill each pathogen. When the macrophages capacity to clear bacteria is overwhelmed macrophages play important roles in orchestrating the inflammatory response through pattern recognition receptor-mediated responses. Macrophages also ensure the inflammatory response is tightly constrained, to avoid tissue damage, and play an important role in downregulating the inflammatory response once initial bacterial replication is controlled.

The mononuclear phagocyte system in homeostasis and disease: a role for heme oxygenase-1

SIGNIFICANCE

Heme oxygenase-1 (HO-1) is a potential therapeutic target in many diseases, especially those mediated by oxidative stress and inflammation. HO-1 expression appears to regulate the homeostatic activity and distribution of mononuclear phagocytes (MP) in lymphoid tissue under physiological conditions. It also regulates the ability of MP to modulate the inflammatory response to tissue injury.

RECENT ADVANCES

The induction of HO-1 within MP-particularly macrophages and dendritic cells-modulates the effector functions that they acquire after activation. These effector functions include cytokine production, surface receptor expression, maturation state, and polarization toward a pro- or anti-inflammatory phenotype. The importance of HO-1 in MP is emphasized by their expression of specific receptors that primarily function to ingest heme-containing substrate and deliver it to HO-1.

CRITICAL ISSUES

MP are the first immunological responders to tissue damage. They critically affect the outcome of injury to many organ systems, yet few therapies are currently available to specifically target MP during disease pathogenesis. Elucidation of the role of HO-1 expression in MP may help to direct broadly applicable therapies to clinical use that are based on the immunomodulatory capabilities of HO-1.

FUTURE DIRECTIONS

Unraveling the complexities of HO-1 expression specifically within MP will more completely define how HO-1 provides cytoprotection in vivo. The use of models in which HO-1 expression is specifically modulated in bone marrow-derived cells will allow for a more complete characterization of its immunoregulatory properties.

Sir Marc Armand Ruffer and Giulio Bizzozero: the first reports on efferocytosis

Review of the discovery of efferocytosis.

Sir Marc Armand Ruffer, a physician and a bacteriologist, well-known for his discoveries in paleopathology, and Giulio Bizzozero, an Italian pathologist, famous for his work on platelets, have made significant contributions in the field of phagocytosis. They both reported among the very first descriptions of efferocytosis.

The historical milestones in the understanding of leukocyte biology initiated by Elie Metchnikoff

Progress in science is made with key discoveries, correct analyses, wrong statements, and disputes within the scientific community. Despite scientific controversies, Elie Metchnikoff has allowed the theory of phagocytes to triumph. Starting his career as a zoologist, Metchnikoff became a pathologist, beautifully defining the role of monocytes, macrophages, and neutrophils during inflammation and innate immunity. The discoveries of immune cells were made by other outstandings scientists, such as Paul Ehrlich, whose key contributions to humoral immunity led him to share the Nobel Prize with Metchnikoff. Ludwig Aschoff grouped certain cells under the term RES, according to their propensity for absorbing and storing vital stains. This classification was not always a source of accurate discoveries, and research on the exact function of RES cells led to some wanderings. This is illustrated by studies about the nature of the antibody-producing cells, which were first thought to belong to the RES, before being identified as plasmocytes and lymphocytes.

The evolution of the understanding of sepsis, infection, and the host response: a brief history

An appreciation for the problem of sepsis starts at the very beginning of recorded time. Early writings from the Middle East, China, and Greece indicate that waves of epidemics and sudden death in previously healthy people were noted as having special significance long before the germ theory of disease was first postulated. This article focuses on the evolution of understanding about the fundamental nature of infection and the host response that leads to sepsis.

A Brief History of Microbiology and Immunology

Vaccine history is inextricably linked with the histories of microbiology and immunology; evolution of the latter disciplines parallels the ongoing quest of humankind to understand the fundamental basis of life. How our species survives in the hostile world that surrounds us has been a source of fascination since the beginning of recorded time. Injury and infection likely exacted a heavy toll as our early hominid ancestors descended from the trees and adapted a predatory life style on the African plains; death from bleeding and wound infections undoubtedly plagued early humans (Opal 2003). Epidemic disease, however, probably played a minor role in shaping the primitive human immune system. Instead, the primary determinants of lethality for small, scattered bands of hunter-gatherer populations of Homo sapiens were starvation, predation, and hypothermia.

The macrophage: past, present and future

As we approach the centenary of Elie Metchnikoff's Nobel Prize (1908), it is opportune to reflect upon the history of macrophage immunobiology, take stock of current knowledge and anticipate questions for the future. Starting from his appreciation of phagocytosis as an important determinant of host defence against infection and injury, we have learned a great deal about the distribution of macrophages throughout the body, their heterogeneous phenotype and complex functions in tissue homeostasis as well as in innate and acquired immunity. Recent discoveries of Toll-like and other plasma membrane, vacuolar and cytosolic recognition molecules have brought the macrophage and closely related dendritic cells to the centre of immunologic attention, but many earlier discoveries of their cellular and molecular properties have laid a broader foundation to the appreciation of their remarkable plasticity and adaptability to local and systemic cues. Discoveries of pro-inflammatory mediators such as TNF and other secretory products have provided valuable insights into the role of macrophages in many acute and chronic disease processes, and led to the development of effective therapeutics. Much remains to be discovered regarding both their specific functions and by study of their general cellular properties, in vitro and in vivo.

Early events in innate immunity in the recognition of microbial pathogens

Innate immunity is characterised by a rapid action of host effector molecules and leukocytes aimed at limiting the multiplication of invading microbial organisms and destroying them. The recognition and destruction of microorganisms involves humoral factors (e.g., the complement system and natural antibodies) and different cell types (e.g., phagocytic cells, mast cells, natural killer cells). Microbial detection by cells involves germ line-encoded pattern-recognition receptors such as Toll-like receptors and nucleotide-binding oligomerization domain-like receptors. Cellular activation by pathogens leads to the release of antimicrobial peptides (e.g., defensins and peptidoglycan recognition proteins) and cytokines that orchestrate the anti-infectious response. Cytokines enhance phagocytosis and leukocyte microbicidal activity, allow cellular recruitment into the infectious focus, boost hematopoiesis, induce fever and lead to the production of acute phase proteins.