Biomedical subjects

A E Ellis

Publications and source records attributed to A E Ellis.

75 records · Page 5Linked to original sources

PubMedDate not supplied

Generation of primary monocyte-like cultures from rainbow trout head kidney leukocytes.

Trout primary kidney monocyte-like cultures (T-PKM) were generated by incubating head kidney leukocytes in the presence of cell-conditioned medium (CCM). This technique was adapted from procedures that were previously used to cultivate in vitro-derived kidney macrophages (IVDKM) from the goldfish. Flow cytometric analysis of the initial T-PKM cultures, identified three cell sub-populations, but only one of these sub-populations survived extensive cultivation periods (i.e. >8 days) in the presence of CCM. Functionally, reactive oxygen intermediate (ROI) production was detected following stimulation of T-PKM with PMA. However, these cells failed to produce reactive nitrogen intermediates (RNI) in response to immunological stimuli. In contrast, goldfish IVDKM were capable of producing both ROI and RNI. Using the dihydrorhodamine (DHR) assay and flow cytometry, we identified two ROI-producing sub-populations in goldfish IVDKM but only a single ROI-producing sub-population was present after extended cultivation of T-PKM. This T-PKM sub-population was subsequently sorted using the flow cytometer and shown to possess monocyte-like morphology by microscopic and cytometric analysis. Thus, acquisition of antimicrobial functions following cultivation of kidney leukocytes of rainbow trout and goldfish is markedly different, and may be due to the failure of trout monocyte-like cells to undergo a final differentiation step in vitro.

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PubMedDate not supplied

Innate host defense mechanisms of fish against viruses and bacteria.

The integumental defenses provide a physical and chemical barrier to the attachment and penetration of microbes. Besides the entrapping and sloughing of microbes in the mucus, the latter contains many antibacterial substances including anti-bacterial peptides, lysozyme, lectins and proteases. The gastro-intestinal tract is a hostile environment of acids, bile salts and enzymes able to inactivate and digest many viruses and bacteria. In most cases the integumental defenses are sufficient to protect against even quite virulent organisms which often only produce disease when the integument has been physically damaged. If a microbe gains access to the tissues of the fish, it is met with an array of soluble and cellular defenses. The complement system, present in the blood plasma, plays a central role in recognising bacteria and its activated products may lyse the bacterial cells, initiate inflammation, induce the influx of phagocytes and enhance their phagocytic activity. Complement can be activated directly by bacterial products and constituents and also indirectly by other factors, principally C-reactive protein and lectins, which can also bind to the bacterial surface. Plasma also contains a number of factors which inhibit bacterial growth(e.g. transferrin and anti-proteases) or which are bactericidal e.g. lysozyme. Following the infection of fish with virus pathogens, infected cells produce interferon. This induces antiviral defenses in neighbouring cells which are then protected from becoming infected. Anti-viral cytotoxic cells are able to lyse virally infected cells and thus reduce the rate of multiplication of virus within them. Innate defenses thus provide a pre-existing and fast-acting system of protection which is non-specific and relatively temperature-independent and thus has several advantages over the slow-acting and temperature-dependent specific immune responses.

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PubMedDate not supplied

Binding of immune complexes to Atlantic salmon peripheral blood leucocytes.

The ability of peripheral blood leucocytes (PBL) of Atlantic salmon to bind immune complexes in an antibody-dependent fashion was investigated. Immune complexes were labelled with fluorescein isothiocyanate and binding of these complexes to isolated PBL was determined by flow cytometry. The data show that a high proportion (up to 65%) of PBL were capable of binding immune complexes, and this binding did not occur when immune serum was replaced with normal serum. The presence of fresh normal serum inhibited or abrogated immune complex-binding of PBL. This is the first report of high levels of immune complex receptors on leucocytes in fish, and the dependence of complex binding on the presence of antibody suggests that these receptors may be similar to Fc receptors which are widely distributed on immunocytes of mammals.

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