Modulation of granulocyte responses in three-spined sticklebacks Gasterosteus aculeatus infected with the tapeworm Schistocephalus solidus

Abstract

Leukocytes isolated from the head kidney and peripheral blood of 3-spined sticklebacks Gasterosteus aculeatus L. were analysed by means of flow cytometry during infection with the tapeworm Schistocephalus solidus (Müller, 1776). Although parasites increased their body weight continuously throughout the observation period (98 d), proportions of granulocytes increased in blood and head kidney only up to Day 63 post-infection (p.i.). Thereafter, declining proportions of granulocytes were observed in both organs. Thus the relative decrease in granulocyte number was not correlated to a decline in the parasitic load of the fish. To investigate a possible modulatory impact of S. solidus on granulocyte function, head kidney leukocytes were isolated at times before Day 63 p.i. and tested in vitro for their capacity to produce reactive oxygen species (ROS). Head kidney leukocytes from S. solidus-infected fish, analysed immediately after isolation (ex vivo, Day 40 p.i.), exhibited a higher ROS production when stimulated with phorbol myristate acetate (PMA), than leukocytes from naïve, sham-treated control fish and fish that had resisted or cleared the infection (exposed but not infected). The latter showed an increased spontaneous ROS production that was not correlated to the numbers of granulocytes present in the head kidney isolates. In infected sticklebacks, spontaneous and PMA-induced ROS production was significantly correlated with numbers of granulocytes present in the head kidney isolates, suggesting that elevated ROS production was due to higher numbers of responding cells rather than an increased capacity of single cells. In vitro, after cultivation for 4 d in the presence of pokeweed mitogen (PWM) or extracts from S. solidus, head kidney leukocytes from control fish showed an increased ROS production and phagocytic activity compared with nonstimulated control cultures. In contrast, head kidney leukocytes from infected fish isolated on Days 48 and 44 p.i., failed to respond to S. solidus antigens in vitro. During S. solidus infection, granulocyte mobilisation resulted in elevated numbers of these cells in head kidneys, but the lack of an in vitro response to S. solidus antigens indicates an in vivo priming of granulocytes by the parasite. These observations may reflect the ability of S. solidus to impair the host's immune response once the parasite is developing in the body cavity of G. aculeatus.

Molecular profiling of the gilthead sea bream (Sparus aurata L.) response to chronic exposure to the myxosporean parasite Enteromyxum leei

“…In a subsequent study investigating the effects of gilthead sea bream nutritional status on E. leei disease progression, total serum peroxidases, lysozyme and nitric oxide were also significantly reduced in exposed fish fed either fish oil or a vegetable oil-based diet (Estensoro et al, 2011). Other immune parameters such as the phagocytic activity of macrophages and/or respiratory burst of leukocytes were also decreased in different hosts infected with other parasites (Mustafa et al, 2000;Fast et al, 2002;Scharsack et al, 2004;Karagouni et al, 2005). At the transcriptional level, the parasite-mediated amoebic gill disease (AGD) in Atlantic salmon produced a marked up-regulation of gene expression in early stages (4-8 days) of infection (Morrison et al, 2006), whereas at medium (19 days) (Wynne et al, 2008a) and long term exposure (36 days) (Young et al, 2008), a strong overall gene suppression was evident in the immune response, transport, translation and catalytic activity functional categories.…”

Heat and immunity: an experimental heat wave alters immune functions in three‐spined sticklebacks (Gasterosteus aculeatus)

“…leucocytes (HKL) were prepared by forcing the head kidney tissues through the cell strainers. Isolated HKL were washed twice (5 min 600 9 g) with R-90 and resuspended in a final volume of 500 lL (Scharsack et al 2004). Body condition index (BCI) = 100 9 [weight fish/length fish (slope of regression) ] and splenosomatic index (SSI) = 100 9 (weight spleen/weight fish) were calculated.…”

Who is in control of the stickleback immune system: interactions between Schistocephalus solidus and its specific vertebrate host

“…Briefly, total cell numbers in individual HKL isolates were determined by means of flow cytometry with the standard cell dilution assay (Pechhold et al 1994) as modified by Scharsack et al (2004). Suspensions of HKL were adjusted to 1.2!10 5 viable cells per millilitre with RPMI 1640 diluted with 10% (v/v) distilled water (R-90).…”

“…It also interferes with cell-mediated immunity, since leucocytes isolated from infected sticklebacks failed to respond to S. solidus antigens in vitro (Scharsack et al 2004). The stickleback immune system on the other side should eliminate the tapeworm as early in infection as possible, since this will be potentially impossible later during infection due to the dramatic increase in parasite size.…”