Innate lymphoid cells (ILCs) in teleosts against data on ILCs in humans.

It is assumed that cells corresponding to innate lymphoid cells (ILCs) in humans, in addition to lymphoid tissue inducer cells (LTi), are also found in teleosts. In this systematic group of organisms, however, they are a poorly understood cell population. In contrast to the data on ILCs in humans, which also remain incomplete despite advanced research, in teleosts, these cells require much more attention. ILCs in teleosts have been presented as cells that may be evolutionary precursors of NK cells or ILCs identified in mammals, including humans. It is a highly heterogeneous group of cells in both humans and fish and their properties, as revealed by studies in humans, are most likely to remain strictly dependent on the location of these cells and the physiological state of the individual from which they originate. They form a bridge between innate and adaptive immunity. The premise of this paper is to review the current knowledge of ILCs in teleosts, taking into account data on similar cells in humans. A review of the knowledge concerning these particular cells, elements of innate immunity mechanisms as equivalent to, or perhaps dominant over, adaptive immunity mechanisms in teleosts, as presented, may inspire the need for further research.

Virophages-Known and Unknown Facts.

The paper presents virophages, which, like their host, giant viruses, are "new" infectious agents whose role in nature, including mammalian health, is important. Virophages, along with their protozoan and algal hosts, are found in fresh inland waters and oceanic and marine waters, including thermal waters and deep-sea vents, as well as in soil, plants, and in humans and animals (ruminants). Representing "superparasitism", almost all of the 39 described virophages (except Zamilon) interact negatively with giant viruses by affecting their replication and morphogenesis and their "adaptive immunity". This causes them to become regulators and, at the same time, defenders of the host of giant viruses protozoa and algae, which are organisms that determine the homeostasis of the aquatic environment. They are classified in the family Lavidaviridae with two genus (Sputnikovirus, Mavirus). However, in 2023, a proposal was presented that they should form the class Maveriviricetes, with four orders and seven families. Their specific structure, including their microsatellite (SSR-Simple Sequence Repeats) and the CVV (cell-virus-virophage, or transpovirion) system described with them, as well as their function, makes them, together with the biological features of giant viruses, form the basis for discussing the existence of a fourth domain in addition to Bacteria, Archaea, and Eukaryota. The paper also presents the hypothetical possibility of using them as a vector for vaccine antigens.

Immunity of the intestinal mucosa in teleost fish.

The paper presents the problem of intestinal mucosa immunity in teleost fish. The immunity of the intestinal mucosa in teleost fish depends on the elements and mechanisms with different organizational/structural and functional properties than in mammals. The organization of the elements of intestinal mucosal immunitya in these animals is associated with the presence of immune cells that fulfil the functions assigned to the induction and effector sites of mucosal immunity in mammals; they are located at various histological sites of the mucosa - in the lamina propria (LP) and in the surface epithelium. The presence of mucosa-associated lymphoid tissue (MALT) has not been demonstrated in teleost fish, and the terminology used in relation to the structure and function of the mucosa immunity components in teleost fish is inadequate. In this article, we review the knowledge of intestinal mucosal immunity in teleost fish, with great potential for knowledge and practical applications especially in the field of epidemiological safety. We discuss the organization and functional properties of the elements that determine this immunity, according to current data and taking into account the tissue definition and terminology adopted by the Society for Mucosal Immunology General Assembly (13th ICMI in Tokyo, 2007).

Haematopoiesis in Zebrafish (Danio Rerio).

Haematopoiesis in fish and mammals is a complex process, and many aspects regarding its model and the differentiation of haematopoietic stem cells (HSCs) still remain enigmatic despite advanced studies. The effects of microenvironmental factors or HSCs niche and signalling pathways on haematopoiesis are also unclear. This review presents Danio rerio as a model organism for studies on haematopoiesis in vertebrates and discusses the development of this process during the embryonic period and in adult fish. It describes the role of the microenvironment of the haematopoietic process in regulating the formation and function of HSCs/HSPCs (hematopoietic stem/progenitor cells) and highlights facts and research areas important for haematopoiesis in fish and mammals.

What Function Do Platelets Play in Inflammation and Bacterial and Viral Infections?

The article presents the function of platelets in inflammation as well as in bacterial and viral infections, which are the result of their reaction with the endovascular environment, including cells of damaged vascular endothelium and cells of the immune system. This role of platelets is conditioned by biologically active substances present in their granules and in their specific structures - EV (extracellular vesicles).

Immunological memory in teleost fish.

Immunological memory can be regarded as the key aspect of adaptive immunity, i.e. a specific response to first contact with an antigen, which in mammals is determined by the properties of T, B and NK cells. Re-exposure to the same antigen results in a more rapid response of the activated specific cells, which have a unique property that is the immunological memory acquired upon first contact with the antigen. Such a state of immune activity is also to be understood as related to "altered behavior of the immune system" due to genetic alterations, presumably maintained independently of the antigen. It also indicates a possible alternative mechanism of maintaining the immune state at a low level of the immune response, "directed" by an antigen or dependent on an antigen, associated with repeated exposure to the same antigen from time to time, as well as the concept of innate immune memory, associated with epigenetic reprogramming of myeloid cells, i.e. macrophages and NK cells. Studies on Teleostei have provided evidence for the presence of immunological memory determined by T and B cells and a secondary response stronger than the primary response. Research has also demonstrated that in these animals macrophages and NK-like cells (similar to mammalian NK cells) are able to respond when re-exposed to the same antigen. Regardless of previous reports on immunological memory in teleost fish, many reactions and mechanisms related to this ability require further investigation. The very nature of immunological memory and the activity of cells involved in this process, in particular macrophages and NK-like cells, need to be explained. This paper presents problems associated with adaptive and innate immune memory in teleost fish and characteristics of cells associated with this ability.

Type I interferons in ray-finned fish (Actinopterygii).

Interferons (IFNs) are proteins of vital importance in the body's immune response. They are formed in different types of cells and have been found in fish, amphibians, reptiles and mammals. Two types of IFN have been found in ray-finned fish (Superclass: Osteichthyes, Class: Actinopterygii) so far, i.e. IFN type I (IFN I) and IFN type II (IFN II), while the presence of IFN type III (IFN III), which is found in phylogenetically older cartilaginous fishes, was not confirmed in this taxonomic group of vertebrates. Currently, type I IFN in Actinopterygii is divided into three groups, I, II and III, within which there are subgroups. These cytokines in these animals show primarily antiviral activity through the use of a signalling pathway JAK-STAT (Janus kinases - Signal transducer and activator of transcription) and the ability to induce ISG (IFN-stimulated genes) expression, which contain ISRE complexes (IFN-stimulated response elements). On the other hand, in Perciformes and Cyprinidae, it was found that type I/I interferons also participate in the antimicrobial response, inter alia, by inducing the expression of the inducible nitric oxide synthase (iNOS) and influencing the production of reactive oxygen species (ROS) in cells carrying out the phagocytosis process.

Immune Functions of Erythrocytes in Osteichthyes.

Red blood cells (RBCs)-erythrocytes-of Osteichthyes are primarily known for their involvement in the process of gas exchange and respiration. Currently, physiological properties of RCBs in fish should also include their ability to participate in defense processes as part of the innate and adaptive immune mechanisms. In response to viruses, bacteria, and fungi or recombinant nanoparticles, they can modulate expression of genes responsible for immune reactions, influence activity of leukocytes, and produce cytokines, antimicrobial peptides, and paracrine intercellular signaling molecules. Via the complement system (CR1 receptor) and owing to their phagocytic properties (erythrophagocytosis), RBCs of Osteichthyes can eliminate pathogens. In addition, they are probably involved in the immune response as antigen-presenting cells via major histocompatibility complex class II antigens.

Major Histocompatibility Complex in Osteichthyes.

Based on analysis of available genome sequences, five gene lineages of MHC class I molecules (MHC I-U, -Z, -S, -L and -P) and one gene lineage of MHC class II molecules (MHC II-D) have been identified in Osteichthyes. In the latter lineage, three MHC II molecule sublineages have been identified (MHC II-A, -B and -E). As regards MHC class I molecules in Osteichthyes, it is important to take note of the fact that the lineages U and Z in MHC I genes have been identified in almost all fish species examined so far. Phylogenetic studies into MHC II molecule genes of sublineages A and B suggest that they may be descended from the genes of the sublineage named A/B that have been identified in spotted gar (Lepisosteus oculatus). The sublineage E genes of MHC II molecules, which represent the group of non-polymorphic genes with poor expression in the tissues connected with the immune system, are present in primitive fish, i.e. in paddlefish, sturgeons and spotted gar (Lepisosteus oculatus), as well as in cyprinids (Cyprinidae), Atlantic salmon (Salmo salar), and rainbow trout (Oncorhynchus mykiss). Full elucidation of the details relating to the organisation and functioning of the particular components of the major histocompatibility complex in Osteichthyes can advance the understanding of the evolution of the MHC molecule genes and the immune mechanism.

Melanomacrophages and melanomacrophage centres in Osteichthyes.

Melanomacrophages (MMs) are phagocytizing cells with high amounts of pigments including melanin which can be found in a number of cold-blooded species. In Osteichthyes, these cells cluster to form so-called melanomacrophage centres (MMCs), which are predominantly present in the stroma of hematopoietic and lymphoid tissues, that is, in the kidney and spleen. The functionality of MMs and MMCs results from their involvement and role in the defence reactions, related to both the innate and the adaptive immune mechanisms, and in processes unrelated to defence functions as well. There is evidence that MMCs are structurally and functionally similar to mammals' germinal centres (GCs). It appears that mature IgM+ B cells in Osteichthyes can be the equivalent of mIgM+ centrocytes in mammals, whereas MMs can be, in terms of the function, the equivalent of follicular dendritic cells (FDCs), and MMCs can be, in terms of clustered specific cells, the equivalent of GCs. This paper presents selected facts about the structural and functional similarity between GCs and MMCs and about the involvement and role of MMCs and MMs in the immune response. The facts help get a proper picture of the location of MMs and MMCs within the structure of the fish immune system, also in the context of their evolutionary relationship with GCs and of the possibility of pointing out the evolutionary closeness between MMCs in Osteichthyes and GCs in mammals.

Characterisation of Thrombocytes in Osteichthyes.

Thrombocytes in vertebrates other than mammals, inter alia in fish, are analogues of platelets in mammals. In Osteichthyes, these cells take part in haemostatic processes, including aggregation and release reactions in cases of blood vessel damage, and in the immune response development as well. This paper discusses the development of thrombocytes in Osteichthyes, taking into account the need to make changes to the concept of grouping progenitor cells as suggested in the literature. The following pages present the morphological and cytochemical properties of thrombocytes as well as their defence functions, and also point out differences between thrombocytes in fish and platelets in mammals. The paper further highlights the level of thrombocytes' immune activity observed in fish and based on an increased proportion of these cells in response to antigenic stimulation, on morphological shifts towards forms characteristic of dendritic cells after antigenic stimulation and on the presence of surface structures and cytokines released through, inter alia, gene expression of TLR receptors, MHC class II protein-coding genes and pro-inflammatory cytokines. The study also points out the need to recognise thrombocytes in Osteichthyes as specialised immune cells conditioning non-specific immune mechanisms and playing an important role in affecting adaptive immune mechanisms.

Specific humoral immunity in Osteichthyes.

The fish immune system is extremely complex and has considerable adaptive potential. In Osteichthyes, the system is formed by lymphopoietic organs which are important for the differentiation and maturation of the immune system cells. These organs include the anterior kidney (phronephros), the thymus, the spleen, the posterior kidney (mesonephros), and mucosa-associated lymphoid tissues (MALT). Apart from the lymphocytic organs and the MALT system, the immune system components include defensive cells and their products. Those identified in fish include, inter alia, monocytes/macrophages, melanomacrophages, neutrophilic granulocytes, thrombocytes, B cells, plasma cells, and T cells. The roles of the individual components of the organisation of the immune system, the organs, and lymphoid tissue as well as the constituents conditioning the innate and adaptive immunity mechanisms are considered equally important, especially in the context of functional interdependence. The progress in the exploration of the processes of specific humoral immunity in Osteichthyes and the possibilities of their practical application is increasingly promising in view of the expected need for protection of fish against diseases. The paper discusses selected issues concerning recent knowledge about haematopoiesis of B cells, plasmablasts, plasma cells, and immunoglobulins (IgM, IgD, IgT/IgZ).

Comparison of Commensal Escherichia coli Isolates from Adults and Young Children in Lubuskie Province, Poland: Virulence Potential, Phylogeny and Antimicrobial Resistance.

Commensal Escherichia coli population is a dynamic structure which may be important in the pathogenesis of extraintestinal infections. The aim of this study was the comparison of genetic diversity of commensal E. coli isolates from two age group-adults and young children. E. coli strains were isolated on MacConkey agar and identified by biochemical tests. Determination of four major phylogenetic groups, identification of virulence genes and antimicrobial resistance determinants were performed by using multiplex or simplex PCR. Phenotypic analysis of resistance was based on disc-diffusion method. The prevalence of virulence genes was significantly higher among isolates from adults than from young children. Phylogroup B2 predominated among E. coli from adults, whereas phylogroup A was the most common in isolates from young children. The analyses of antimicrobial resistance revealed that resistance to at least one antimicrobial agent and multidrug-resistance were detected significantly more frequent in the isolates from adults than from young children. This study documented that the commensal E. coli isolates from adults showed greater genetic diversity than from young children and constitutes a substantial reservoir of the virulence genes typical for extraintestinal pathogenic E. coli.

Antimicrobial resistance in commensal Escherichia coli from pigs during metaphylactic trimethoprim and sulfamethoxazole treatment and in the post-exposure period.

The prevalence of trimethoprim (TMP) and sulfamethoxazole (SMX) resistance in commensal E. coli from pigs was tested in this study. E. coli was derived from three groups of piglets in successive stages of metaphylactic therapy and from two groups of sows 10 and 18 weeks after the treatment. MIC values of TMP and SMX were determined for a total of 352 strains. The presence of resistance genes (dfrA1, dfrA5, dfrA7, dfrA12, dfrA17, sul1, sul2, sul3) and class 1 and 2 integron-associated dfrA gene cassettes was tested. Resistance to TMP was very high during the administration of the antimicrobial (from 97 to 100%) and amounted to 86% and 69% in the post-exposure period; MIC > 32 mg/L. The isolates from all groups of pigs were resistant to sulfamethoxazole, with MIC > 1028 mg/L. The dfrA1 and sul1 genes (as part of integrons) dominated in E. coli from piglets, but the dfrA12 and sul1 genes were prevalent in E. coli from sows. Coexistence of the different dfrA genes was detected in 71 isolates from all groups of swine. Transcription analysis revealed that most of these genes were not transcribed, particularly gene cassettes of class 1 integrons. The research revealed a high level of resistance associated with the metaphylactic treatment, persistence and circulation of resistance in bacterial populations. Diverse genetic background with multiple and not transcribed resistance genes was observed.

Prevalence of virulence determinants and antimicrobial resistance among commensal Escherichia coli derived from dairy and beef cattle.

Cattle is a reservoir of potentially pathogenic E. coli, bacteria that can represent a significant threat to public health, hence it is crucial to monitor the prevalence of the genetic determinants of virulence and antimicrobial resistance among the E. coli population. The aim of this study was the analysis of the phylogenetic structure, distribution of virulence factors (VFs) and prevalence of antimicrobial resistance among E. coli isolated from two groups of healthy cattle: 50 cows housed in the conventional barn (147 isolates) and 42 cows living on the ecological pasture (118 isolates). The phylogenetic analysis, identification of VFs and antimicrobial resistance genes were based on either multiplex or simplex PCR. The antimicrobial susceptibilities of E. coli were examined using the broth microdilution method. Two statistical approaches were used to analyse the results obtained for two groups of cattle. The relations between the dependent (VFs profiles, antibiotics) and the independent variables were described using the two models. The mixed logit model was used to characterise the prevalence of the analysed factors in the sets of isolates. The univariate logistic regression model was used to characterise the prevalence of these factors in particular animals. Given each model, the odds ratio (OR) and the 95% confidence interval for the population were estimated. The phylogroup B1 was predominant among isolates from beef cattle, while the phylogroups A, B1 and D occurred with equal frequency among isolates from dairy cattle. The frequency of VFs-positive isolates was significantly higher among isolates from beef cattle. E. coli from dairy cattle revealed significantly higher resistance to antibiotics. Some of the tested resistance genes were present among isolates from dairy cattle. Our study showed that the habitat and diet may affect the genetic diversity of commensal E. coli in the cattle. The results suggest that the ecological pasture habitat is related to the increased spreading rate of the VFs, while the barn habitat is characterised by the higher levels of antimicrobial resistance among E. coli.

Type 1 fimbriae in commensal Escherichia coli derived from healthy humans.

Type 1 fimbriae are one of the most important factors of Escherichia coli adaptation to different niches in the host. Our study indicated that the genetic marker--fimH gene occurred commonly in commensal E. coli derived from healthy humans but expression of the type 1 fimbriae was not observed. Identification of fim structural subunit genes (fimA-fimH) and recombinase fimE and fimB genes showed that many of the strains were carrying an incomplete set of genes and the genes expression study revealed that in strains with complete set of fim genes, the fimC gene, encoding the chaperone protein, was not expressed.

Age as a factor influencing diversity of commensal E. coli microflora in pigs.

Commensal, intestinal E. coli microflora plays a role in maintenance of intestinal balance of the host, is responsible for defending against pathogenic E. coli. This study encompasses the analysis of BOX-PCR fingerprinting patterns, phylogenetic grouping and virulence genes prevalence among commensal E. coli isolates derived from healthy pigs. Altogether, 274 unique E. coli isolates were identified, 110 from weaned piglets (Piglets I and Piglets II) and 164 from adult sows (Sows I and Sows II). BOX-PCR analysis distinguished isolates from pigs in different age and indicated that during maturation the changes in E. coli microflora occurred. Phylogenetic grouping revealed significant differences between distribution of four phylogenetic groups among isolates derived from piglets and sows. In phylogenetic structure of isolates from the piglets group B1 prevailed significantly, while among isolates derived from the sows the majority of them were classified into phylogenetic group A. The identification of 17 virulence factors in E. coli isolates derived from healthy pigs was performed. Three of 13 intestinal (escV, ehxA, estII) and four extra-intestinal virulence genes (VGs) (hlyA, fimH, papA, sfaS) were detected in the porcine isolates. The percentage of VGs positive isolates among piglets is higher than among sows, moreover, the VGs occurring in E. coli isolates from piglets revealed greater diversity than that detected among isolates from sows.

The phenotypic and genotypic characteristics of antibiotic resistance in Escherichia coli populations isolated from farm animals with different exposure to antimicrobial agents.

The aim of the study was to determine the influence of the presence or the absence of antibiotic input on the emergence and maintenance of resistance in commensal bacteria from food producing animals. The research material constituted E. coli isolates from two animal species: swine at different age from one conventional pig farm with antibiotic input in young pigs and from beef and dairy cattle originated from organic breeding farm. The sensitivity to 16 antimicrobial agents was tested, and the presence of 15 resistance genes was examined. In E. coli from swine, the most prevalent resistance was resistance to streptomycin (88.3%), co-trimoxazole (78.8%), tetracycline (57.3%) ampicillin (49.3%) and doxycycline (44.9%) with multiple resistance in the majority. The most commonly observed resistance genes were: bla(TEM) (45.2%), tetA (35.8%), aadA1 (35.0%), sul3 (29.5%), dfrA1 (20.4%). Differences in phenotypes and genotypes of E. coli between young swine undergoing prevention program and the older ones without the antibiotic pressure occurred. A disparate resistance was found in E. coli from cattle: cephalothin (36.9%), cefuroxime (18.9%), doxycycline (8.2%), nitrofurantoin (7.7%), and concerned mainly dairy cows. Among isolates from cattle, multidrug resistance was outnumbered by resistance to one or two antibiotics and the only found gene markers were: bla(SHV), (3.4%), tetA (1.29%), bla(TEM) (0.43%) and tetC (0.43%). The presented outcomes provide evidence that antimicrobial pressure contributes to resistance development, and enteric microflora constitutes an essential reservoir of resistance genes.