Abstract
The immunostimulant effect of α-glucans microparticles has been tested in vertebrates to increase protection against pathogens and prevent lethal diseases, however, the effect of these particles on invertebrate organisms has not been evaluated yet. In the present report, Cherax quadricarinatus crayfish was stimulated with raw starch microparticles (SMP, 200 ng/mL), Vibrio parahaemolyticus N16 (Vp, 1 × 10(9) cells/mL) and Escherichia coli BL21A1 (Ec, 1 × 10(9) cells/mL) to evaluate hemocyte subpopulations, phagocytosis activity, ROS production, and glycosylation patterns, as markers of immune mechanisms activation. Hyaline cells decreased after 4 h of SMP and Vp stimulation, and the phagocytosis slightly increased in this subpopulation with SMP and bacteria stimuli, however, there was no significant increase in ROS production; after 4 h with SMP and bacteria stimuli. The number of semigranular cells was not modified after 4 h of SMP stimulation compared to control meanwhile with Vp and Ec significantly decreased; phagocytosis and ROS production were increased in all stimuli. Granular cells were increased after 4 h with all stimuli, phagocytosis of SMP was the highest among all stimuli meanwhile ROS production was higher in bacteria stimuli. Glycosylation patterns of hemocyte membranes appear to be associated with the activation state of immune cells, as modifications in glycan expression impact their immune functions. In hyaline cells, a decrease in oligomannose and α-2,6-linked sialic acid expression was observed, along with an increase in Gal residues. Semigranular cells exhibited reduced GalNAc expression and increased α-2,6-linked sialic acid expression across all stimuli. Granular cells showed decreased Gal and GalNAc expression, while α-2,3- and α-2,6-linked sialic acid expression increased in response to SMP and bacterial stimuli. Our results indicate that SMP, like Vp or Ec, serves as an effective stimulus for activating both cellular and humoral immune mechanisms. These particles could be considered a potential adjuvant or immunostimulant for crustaceans and other invertebrate organisms.