Macrophages as effector cells of protective immunity in murine schistosomiasis

The respiratory burst is not required for killing of intracellular and extracellular parasites by a lymphokine‐activated macrophage cell line

“…Larvacidal activity was determined microscopically after incubation of the schistosomula for 48 h with M a . As previously observed [22], nonactivated pM@ exhibited negligible cytotoxicity against S. mansoni larvae, while significant killing was observed by activated pM@ (96% larvacidal activity) (Table 3). Similarly, nonactivated IC-21 cells exhibited minimal cytotoxicity against larvae.…”

Cytotoxic reactions of rainbow trout, Salmo gairdneri Richardson, macrophages for larvae of the eye fluke Diplostomum spathaceum (Digenea)

“…Consequently, cell : parasite ratios of about 2000 : 1 were used in subsequent experiments, so that optimum cell : parasite contact was achieved. The cytocidal activity of activated macrophages in mammalian systems against schistosomules demonstrates a similar dependence on cell : target ratios (James et al, 1982;Gordon & McLaren, 1988), as do eosinophils (Hagan et al, 1985) and neutrophils (Kazura et al, 1981;Icani & McLaren, 1981). Whether adherence of macrophages to diplostomules is required for parasite killing is unclear in the present study, since macrophages were only seen adhering to dead or dying diplostomules.…”

“…This is quite different from infections of mammals where only activated macrophages are able to kill significant numbers of the post-penetration larvae of similar helminth parasites such as Schistosoma mansoni in vitro (James et al, 1982;Kubelka et al, 1986;Gordon & McLaren, 1988). The killing ability of trout macrophages appears dependent on the cell : parasite ratio which must be greater than 150 : 1 to effect significant levels of parasite mortality.…”

“…Macrophages are a major effector cell in mammalian defence against multicellular parasites, once activated by lymphokines released from antigen-or mitogen-stimulated T-lymphocytes (James et al, 1982(James et al, , 1983Kubelka et al, 1986;James, 1986;Gordon & McLaren, 1988). The phenomenon of the activation of the mammalian macrophage has been extensively reviewed and the biochemical criteria for defining activated macrophages in mammals are well documented (Karnovsky & Lazdins, 1978;North, 198 1;Adams & Hamilton, 1984).…”

“…For instance, the eosinophil is regarded as particularly important in the cellular control of parasitic infections, and in schistosomiasis these cells adhere closely to the parasite tegument and degranulate directly onto it (MacKenzie et al, 1977;Capron et al, 1984;Hagan et al, 1985). The activated macrophage is also an important effector cell in defence against rodent schistosomes (James et al, 1982(James et al, , 1983Kubelka et al, 1986;Gordon & McLaren, 1988;Ward & McLaren, 1988) and can effect progressive internal damage to the parasite following only transient attachment to the schistosomule surface: the worm tegument remains intact, however, in contrast with the events associated with granulocyte-mediated schistosomule killing (McLaren & James, 1985). The importance of activated macrophages in vivo is shown in vaccination studies where immunization protocols that fail to elicit activated larvacidal macrophages also fail to confer resistance to subsequent infection (James, 1986;Lewis et d.. 1987).…”