In vitro antigen-binding properties of coelomocytes of Eisenia foetida (Annelida)

In vitro cultivation of primary intestinal cells from Eisenia fetida as basis for ecotoxicological studies

The earthworm Eisenia fetida is a commonly used model organism for unspecific soil feeders in ecotoxicological studies. Its intestinal cells are the first to encounter possible pollutants co-ingested by the earthworm, which makes them prime candidates for studies of toxic effects of environmental pollutants on the cellular as compared to the organismic level. In this context, the aim of this study was to demonstrate the suitability of preparations of primary intestinal E. fetida cells for in vitro ecotoxicological studies. For this purpose, a suitable isolation and cultivation protocol was established. Cells were isolated directly from the intestine, maintaining >85% viability during subsequent cultivations (up to 144 h). Exposure to established pollutants and soil elutriates comprising silver nanoparticles and metal ions (Cu²⁺, Cd²⁺) induced a significant decrease in the metabolic activity of the cells. In case of microplastic particles (MP particles), namely 0.2, 0.5, 2.0, and 3.0 µm diameter polystyrene (PS) beads as well as 0.5 and 2.0 µm diameter polylactic acid (PLA) beads, no active uptake was observed. Slight positive as well as negative dose and size dependent effects on the metabolism were seen, which to some extent might correlate with effects on the organismic level.

Comparative distribution of urocortin- and CRF-like immunoreactivities in the nervous system of the earthworm Lumbricus terrestris

Corticotropin-releasing factor (CRF) and urocortin (Ucn) are both members of the CRF neuropeptide family. The distribution of Ucn- and CRF-like immunoreactive (ir) structures in the central nervous system of several vertebrate species has been studied, but little is known about that in non-vertebrates. We used a highly specific polyclonal antibody against rat Ucn and CRF to determine and compare the distribution of Ucn- and CRF-like immunoreactivity in the earthworm nervous system. Several Ucn- and CRF-like ir perikarya were described in the cerebral ganglion, subesophageal and ventral cord ganglia. The majority of Ucn-like ir cells were found in the ventral ganglia, whereas CRF-like ir cells were most abundant in the cerebral ganglion. Scattered Ucn- and CRF-like ir varicose fiber terminals were seen in all areas of the earthworm central nervous system. Ucn-like ir cell bodies and fiber terminals were also demonstrated in the pharyngeal wall. No co-localization of Ucn- and CRF-like ir nervous structures were observed. This study provided morphological evidence that Ucn- and CRF-like neurosecretory products exist in the earthworm central nervous system. Furthermore, both the distribution and morphology of Ucn- and CRF-like ir structures were distinct, therefore, it can be hypothesized that these neuropeptides exert different neurendocrine functions in the earthworm nervous system.

Antimicrobial defense of the earthworm

Discrimination of self and nonself is one of the features of all animal species but the ways of elimination of nonself are different. Defense strategies of invertebrates, which lack antibodies and lymphocytes, are based on innate defense mechanisms. The study of such, undoubtedly less complex, defense mechanisms in invertebrates may shed a new light on the more sophisticated immunity of vertebrates. The main aim of this review is to show on one experimental model--an oligochaete annelid--cellular and humoral defense pathways protecting against microbial infection.

Characterization of the limited specificity of antigen recognition in earthworms

Earthworms respond to parenteral stimulation with a protein antigen by the formation of an antigen-binding protein. Earthworms were parenterally stimulated with different proteins and the protein binding was estimated in vitro on both humoral and cellular levels. The binding was significantly higher when the same protein was used for in vivo stimulation. The degree of specificity of the antigen-binding protein after the secondary in vivo challenge increased, but even so it was considerably lower than that of vertebrate immunoglobulins.

A new approach to in vitro studies of antigenic response in earthworms

A method for in vitro cultivation of earthworm gut wall tissue explants is described. Tissue explants are able to respond to protein antigen by secretion of antigen-binding protein into the culture medium. Large irregular cells and round-shaped cells are released from tissue explants during the cultivation. This method represents an advantageous tool for in vitro studies providing the possibility of parallel assays from the same donor.

Antigen processing in earthworms

The administration of protein antigens into earthworms Lumbricus terrestris and Eisenia foetida induces the formation of antigen-binding protein (ABP) with the maximum response occurring between days 4 and 8. High proteolytic activities observed both in coelomocytes and in coelomic fluids cause rapid antigen degradation; the majority of antigen is digested during the first 24 h. To analyze the role of proteolytic processing of antigen in ABP response in vitro, the intact antigen (ARS-HSA) as well as its proteolytic fragments were added to tissue explant cultures and ABP formation followed by indirect ELISA using mAb to ABP. The response to small fragments was comparable to that induced by intact ARS-HSA. Furthermore, the response to intact antigen was almost completely blocked by the non-toxic serine protease inhibitor Pefabloc, while the response to small fragments was only slightly reduced. The kinetics of response to intact antigen significantly differed from that induced by small (< 3 kDa) fragments. We suggest that proteolytic processing is involved in the stimulation of ABP formation.

The fate of protein antigen in earthworms: study in vivo

Parenteral administration of antigen induces in the earthworms Lumbricus terrestris and Eisenia foetida the formation of antigen-binding protein. Labelled antigen was efficiently digested in the coelomic fluids of both species since the total amount of radioactivity in the coelomic fluids decreased. Antigen internalized in the free coelomocytes of both species was present in a TCA-precipitable form, although the decline of total radioactivity was higher than in the coelomic fluid, indicating that the TCA-nonprecipitable fragments are rapidly released from coelomocytes into the coelomic fluid. Within the first 24 h after administration, labelled antigen was detected throughout all tissues except for the epidermis and cuticle, and after 4 days it was found in the chloragogenic tissue around the gut, dorsal vein and typhlosole.

Mitogenicity of the earthworm's (Eisenia foetida) insulin-like proteins

1. Biologically active glycolipoprotein complex (G-90), isolated from whole earthworm tissue extract (Eisenia foetida), was separated into seven fractions by gel-filtration. 2. It has been shown by radioimmunoassay that each of the fractions, except the lightest one, is cross-reactive with porcine anti-insulin antibodies. Molecules that possess such activity were detected by immunoblotting. 3. All fractions, except the heaviest and the lightest one, stimulate mammalian normal and transformed cell proliferation in serum-free conditions in vitro. The intensity of stimulation depends on cell type. Stimulation is completely abolished if the medium is supplemented with fetal calf serum.

Molecules in earthworm coelomic fluid that bind anti-IgA and anti-IgG, but not anti-IgM

Coelomic fluid from the earthworm Lumbricus terrestris is known to contain immunoactive cells and molecules involved in immune defense. To assess the ability of such molecules to form precipitating complexes with anti-human immunoglobulins, radial immunodiffusion experiments were conducted. Anti-human IgG, anti-human IgA, and anti-human IgM were the three immunoglobulins examined. Earthworm coelomic fluid was found to contain molecules that bind anti-IgA and anti-IgG. No precipitation reactions were observed with anti-IgM. Earthworm coelomic fluid diluted 1:8 still formed precipitating complexes with anti-IgA and anti-IgG. Elucidation of the earthworm binding site on anti-IgG and anti-IgA could make earthworm coelomic fluid a valuable reagent in immunological, chemical and biological research.

The fate of protein antigen in earthworms: study in vitro

Earthworm coelomocytes digest protein antigen in vitro. Proteolytic activity was detected both in cell-free coelomic fluid and in cell cultures of free coelomocytes which are effectors of earthworm immunodefense mechanisms. Antigen is cleaved either intracellularly or by proteolytic enzymes released by coelomocytes into the medium. Proteolysis was observed both in non-stimulated and antigen-stimulated cultures. Since significantly higher proteolysis was shown in supernatants from cultures of antigen-stimulated coelomocytes, we can assume that the release of proteolytic enzymes was inducible.

Detection of antigen in the coelomocytes of the earthworm, Eisenia foetida (Annelida)

Earthworms, Eisenia foetida, are able to respond to antigenic stimulation by the formation of the antigen-binding molecules by coelomocytes--the effector cells of annelids' defence reactions. The ability to react with gold-labelled antigen was detected in agranular coelomocytes by electron microscopy. Furthermore, flow cytometry analysis used for quantitative evaluation of antigen binding showed significant increase of both antigen-binding cells and the amount of antigen bound per cell after stimulation. The antigen binding was inhibited by preincubation of cells with several similar proteins, although the most potent inhibitor was the immunizing antigen.