Effect of Biomphalaria straminea plasma in the phagocytosis of Biomphalaria glabrata hemolymph cells.

Abstract

Mollusc defensive system that discriminates self from non self molecules, include fixed cells that can trap particles like endothelial cells, reticular and pore-cells, and circulating elements (WPW Van Der Knaap & ES Loker 1990 Parasitol Today 6: 175-182). Hemocytes, cells with phagocytic capacity, are determinant elements in the resistance or susceptibility of Biomphalaria snails to the trematoda Schistosoma mansoni infection (FS Bezerra et al. 1997 Rev Inst Med Trop S Paulo 39: 197-201). Biomphalaria resistance or susceptibility to S. mansoni infection is well defined as genetically determined (JV Santana et al. 1978 Rev Saude Publ S Paulo 12: 67-77). Allograft of producing amebocyte organ from resistant snails to susceptible ones, enhance its resistance suggesting that the phenomenon is dependent on hemocytes activity (JT Sullivan et al. 1995 J Parasitol 5: 829-33). On the other hand, inoculation of hemolymph from B. tenagophila infected with either S. mansoni or with other trematoda furcocercaria, raised significantly the cellular response of susceptible mollusc (SM Reis et al. 1995 Rev Saude Publ 29: 259-264). Susceptible B. glabrata snails hemocytes made phagocytosis more efficient when latex particles were covered with resistant strains plasma. Furthermore, the results from our laboratory showed that B. straminea, a highly resistant mollusc to S. mansoni infection, is the only parasite host found in many endemic areas of northeast Brazil [FF Amâncio et al. 1989 Mem Inst Oswaldo Cruz (Suppl. I) 84: 253]. Therefore we tried to observe the influence of soluble products from B. straminea plasma in the phagocytic capacity of B. glabrata hemocytes. B. glabrata hemocyte monolayer was prepared from hemolymph, collected through cephalo-podal bleeding and incubated at 22°C during 40 min in humid chamber. After washing, to remove non adherent cells, the monolayers were incubated with 105 cells of yeast (Saccharomyces sp.) for 1 hr at 22°C. The slides were washed to detach non ingested yeast, fixed with methanol and stained with Giemsa. For determination of the phagocytic index, 200 cells per slide were counted. When necessary, B. straminea plasma was previously incubated with the yeast suspension for 1 hr at 22°C. Another procedure was carried out using the plasma previously warmed at 56°C during half an hour (plasma 56). Following this schedule, five groups were done: Group A: monolayer + fresh B. straminea plasma + yeast suspension Group A 56: monolayer + B. straminea plasma 56 + yeast suspension Group B: monolayer + incubated fresh plasma + yeast suspension Group B 56: monolayer + incubated plasma 56 + yeast suspension Group control: monolayer + Hanks + yeast suspension.