Comprehensive phenotyping of peripheral blood monocytes in healthy bovine

The Coding Logic of Interoception

Interoception, the ability to precisely and timely sense internal body signals, is critical for life. The interoceptive system monitors a large variety of mechanical, chemical, hormonal, and pathological cues using specialized organ cells, organ innervating neurons, and brain sensory neurons. It is important for maintaining body homeostasis, providing motivational drives, and regulating autonomic, cognitive, and behavioral functions. However, compared to external sensory systems, our knowledge about how diverse body signals are coded at a system level is quite limited. In this review, we focus on the unique features of interoceptive signals and the organization of the interoceptive system, with the goal of better understanding the coding logic of interoception.

Flow Cytometric Identification and Enumeration of Monocyte Subsets in Bovine and Water Buffalo Peripheral Blood

Monocytes are innate immune system key players with pivotal roles during infection and inflammation. They migrate into tissues and differentiate into myeloid effect cells (macrophages, dendritic cells) which orchestrate inflammatory processes and are interfaces between the innate and adaptive immune responses. Their clinical relevance to health and disease of cattle (Bos taurus) and water buffalo (Bubalus bubalis), two of the most important livestock species, has been highlighted in physiologic (pregnancy) and pathologic (mastitis, metritis, and viral infections) conditions. The existence of three different monocyte subsets in cattle was established by flow cytometry (FC), as follows: classical (cM; CD14⁺⁺ CD16^-/low ), intermediate (intM; CD14^++/+ CD16⁺ ), and non-classical (ncM; CD14^-/low CD16⁺⁺ ) monocytes. FC applications for studying the immune system of cattle and water buffalo still have significant limitations. In this article, we describe some practical approaches to overcome these limitations and, in particular, allow the identification and enumeration of cM, intM, and ncM subpopulations in cattle and buffalo peripheral blood. Indeed, we propose the new procedure lyse/wash/no-centrifugation (L/W/NC) that can be combined with the FC absolute counting procedures and can overcome specific issues of the lyse/no-wash protocols (L/NW). Finally, for the first time, we demonstrated the existence of cM, intM, and ncM monocyte subsets also in the water buffalo, showing some interesting differences with cattle, such as the bubaline cM are mainly CD14^+/++ /CD16⁺ . These subtle differences may influence inflammatory disease regulation in, for example, mastitis and metritis. The upregulation of CD16 expression on cM may reveal different monocyte priming, leading to different functional features of macrophages/dendritic cells in tissues after infection. © 2023 Wiley Periodicals LLC. Basic Protocol: Absolute count of cM, intM, and ncM without compensation Alternate Protocol: Absolute count of cM, intM, and ncM for single laser platform Support Protocol 1: In-house monoclonal antibody labeling using a Pacific Blue^™ kit Support Protocol 2: In-house monoclonal antibody labeling using an Alexa Fluor^® 647 kit Support Protocol 3: Titration of fluorochrome-conjugated antibodies.

In-depth immunophenotyping reveals significant alteration of lymphocytes in buffalo with brucellosis

Water buffalo (Bubalus bubalis) has a prominent position in the livestock industry worldwide but still suffers from limited knowledge on the mechanisms regulating the immune against infections, including brucellosis (BRC), one of the most significant neglected zoonotic diseases of livestock. Seventy-three buffalo were recruited for the study. Thirty-five were naturally infected with Brucella spp. The aims of the study were to (i) verify the cross-reactivity of 16 monoclonal antibodies (mAbs) developed against human, bovine, and ovine antigens; (ii) evaluate lymphocyte subset alterations in BRC positive buffalo; (iii) evaluate the use of the canonical discriminant analysis (CDA), with flow cytometric data, to discriminate BRC positive from negative animals. A new set of eight mAbs (anti CD3e, CD16, CD18, CD45R0, CD79a; CD172a) were shown to cross-react with water buffalo orthologous molecules. BRC positive animals presented a significant (p < 0.0001) decrease in the percentage of PBMC (29.5 vs. 40.3), total, T and B lymphocytes (23.0 vs. 35.5, 19.2 vs. 28.9, 2.6 vs. 5.7, respectively). In contrast, they showed an increase in percentage of granulocytes (65.2 vs. 55.1; p < 0.0001) and B lymphocytes CD21^neg (22.9 vs. 16.1; p = 0.0067), a higher T/B lymphocyte ratio (10.3 vs. 6.4; p = 0.0011) and CD3⁺ /CD21⁺ (14.7 vs. 8.3; p = 0.0005) ratio. The CDA, applied to 33 different flow cytometric traits, allowed the discrimination of all BRC positive from negative buffalo. Although this is a preliminary study, our results show that flow cytometry can be used in a wide range of applications in livestock diseases, including in support of uncertain BRC diagnoses.

Simplified Approaches for the Production of Monocyte-Derived Dendritic Cells and Study of Antigen Presentation in Bovine

Dendritic cells are sentinels of the immune system responsible for the initiation of adaptive immune mechanisms. In that respect, the study of these cells is essential for a full understanding of host response to infectious agents and vaccines. In ruminants, the large blood volume facilitates the isolation of abundant monocytes and their derivation to other antigen-presenting cells such as dendritic cells and macrophages. However, the available protocols for the production of bovine monocyte-derived dendritic cells (moDCs) rely mostly on time-consuming and costly techniques such as density gradient centrifugation and magnetic sorting of cells. In this study, we describe a simplified protocol for the production of bovine moDC using conventional and serum-free media. We also employ moDC produced by this approach to carry out a flow cytometry-based antigen presentation assay adapted to blood fresh or frozen cells. The experimental strategies described here might enable the setup of studies involving a large number of individuals, requiring a large number of dendritic cells, or relying on the utilization of cryopreserved blood cells. These simplified protocols might contribute to the elucidation of cell-mediated immune responses in bovine.

The Impact of the Animal Housing System on Immune Cell Composition and Function in the Blood of Dromedary Camels

Simple Summary

The present study investigated the impacts of a change in animal housing system on selected parameters of the camel immune system. Samples collected from camels during a free-ranging time were compared with samples collected from the same camels during movement-restricted housing. Movement-restricted camels showed elevated myeloperoxidase activity in their serum, a significant shape-change of their neutrophils, and higher reactive oxygen species content in their monocytes and neutrophils. The leukogram pattern of the camels under restricted housing was characterized by increased numbers of neutrophils, eosinophils, lymphocytes, and monocytes. Within the lymphocyte population, only the helper T cells and B cells were expanded in animals under restricted housing. In addition, restricted housing modulated the expression of several cell surface antigens, including monocyte-polarization markers and cell adhesion molecules. Functional analysis of bacterial phagocytosis indicated impaired antibacterial function of phagocytes in camels under restricted housing. In summary, the present study identified significant changes in blood immune cell composition, phenotype, and function in dromedary camels under restricted-housing conditions, and suggests the development of an excitement leukogram in those animals.

Abstract

Background: The dromedary camel (Camelus dromedarius) is an important livestock animal of desert and semi-desert ecosystems. In recent years, several elements of the camel immune system have been characterized. Stress and excitement induced by animal housing represent the most important environmental factors with potential modulatory effects on the immune system. The present study evaluated the impacts of a restricted-housing system on some phenotypic and functional properties of blood leukocytes in dromedary camels. Methods: Immunofluorescence and flow cytometry were used to comparatively analyze samples collected from camels during a free-ranging time and samples collected from the same camels during movement-restricted housing. Results: In comparison to blood samples collected from the camels during the free-ranging time, samples from movement-restricted camels showed elevated serum myeloperoxidase activity, a significant shape-change in their neutrophils, and higher reactive oxygen species content in their monocytes and neutrophils, indicating increased cellular oxidative stress under movement-restricted housing. The leukogram pattern of the camels under restricted housing was characterized by leukocytosis with increased numbers of neutrophils, eosinophils, lymphocytes, and monocytes, resembling an excitement leukogram pattern. Within the lymphocyte population, only the helper T cells and B cells were expanded in animals under restricted housing. The upregulation of CD163 together with the downregulation of MHC-II on monocytes from excited camels indicate a modulatory potential of animal excitement to polarize monocytes toward an anti-inflammatory phenotype. Functional analysis of bacterial phagocytosis indicates an impaired antibacterial function of phagocytes in excited camels. The downregulation of several cell adhesion molecules on leukocytes from excited camels suggests a role for impaired cell adhesion and tissue migration and leukocyte retention in blood in the observed leukocytosis in animals under excitement. Conclusions: The present study identified significant changes in blood immune cell composition, phenotype, and function in dromedary camels under restricted-housing conditions. The observed changes in leukocyte composition suggest the development of an excitement leukogram pattern in camels under movement-restricted housing. To evaluate the clinical relevance of the observed changes in immune cell phenotype and function for the immune competence of camels under restricted housing, further studies are required.

Monocyte biology conserved across species: Functional insights from cattle

Similar to human monocytes, bovine monocytes can be split into CD14^highCD16^- classical, CD14^highCD16^high intermediate and CD14^-/dimCD16^high nonclassical monocytes (cM, intM, and ncM, respectively). Here, we present an in-depth analysis of their steady-state bulk- and single-cell transcriptomes, highlighting both pronounced functional specializations and transcriptomic relatedness. Bulk gene transcription indicates pro-inflammatory and antibacterial roles of cM, while ncM and intM appear to be specialized in regulatory/anti-inflammatory functions and tissue repair, as well as antiviral responses and T-cell immunomodulation. Notably, intM stood out by high expression of several genes associated with antigen presentation. Anti-inflammatory and antiviral functions of ncM are further supported by dominant oxidative phosphorylation and selective strong responses to TLR7/8 ligands, respectively. Moreover, single-cell RNA-seq revealed previously unappreciated heterogeneity within cM and proposes intM as a transient differentiation intermediate between cM and ncM.

Development of an advanced flow cytometry based high-resolution immunophenotyping method to benchmark early immune response in dairy cows

The determination of the somatic cell count of a milk sample is one of the most common methods to monitor udder health of a dairy cow. However, this procedure does not take into account the fact that cells in milk present a great variety of different cell types. The objective of our study was to establish a high-resolution differential cell count (HRDCC) by means of flow cytometry in blood and milk. We were able to detect ten subpopulations among the three main populations of immune cells and to determine their viability. Additionally, blood samples were analyzed for common laboratory biomarkers, i.e. differential blood counts, haptoglobin levels and several metabolic parameters. In this first feasibility study, we used three different vaccines to stimulate the immune system of five healthy cows each. Samples were collected shortly before, in between and after the vaccinations. Using multivariate statistical methods we saw a diagnostic benefit when HRDCCs were included compared to only the standard laboratory parameters. The impacts of all three vaccinations on the immune system were visible in blood HRDCCs as well as in milk HRDCCs. Cluster of Differentiation 8⁺ (CD8⁺) T cells, B cells and monocyte/macrophage subpopulations were among the most important and statistically relevant parameters for all treatments in both biofluids. Moreover, in one of the treatment groups intermediate monocytes showed a significant increase after both vaccinations. Although the use of HRDCC in blood or milk was shown to be highly relevant for early systemic diagnostic, to confirm these subpopulations further investigations in cows of different breed, lactation stage or health status are required.