Lead Induces Different Responses of Two Subpopulations of Phagocytes in the Holothurian Eupentacta fraudatrix

In view of increasing lead pollution(Pb^(2+)) of coastal waters, the compensatory abilities of holothurians need to be assessed. The goal of the work is to clarify the functional and phenotypical differences between two types of phagocytes(P1 and P2) in Eupentacta fraudatrix exposed to Pb(NO_3)_2. It has been shown that 2 mg L^(-1) lead exposure for 48 h increases the number of P2 phagocytes as compared to P1 cells, does not significantly affect cell viability in both P1 and P2 phagocyte fractions, and significantly enhances chromatin condensation in P2 but not in P1 phagocytes. A lead concentration of 4 mg L^(-1) increases the number of P1 phagocytes compared to that of P2 type, and does not change cell viability and chromatin condensation in P1 phagocytes. In the P2 type, it decreases cell viability and does not influence the level of apoptosis. The protection against lead-induced apoptosis is apparently mediated by the activities of antioxidant enzymes, especially glutathione S-transferase. The differences in labeling cell surface receptors of P1 and P2 phagocytes by plant lectins also indicate the specific phenotypic properties of these cells. The results clarify the potential and GSH-dependent mechanisms of immune adaptation in holothurians that have been shortly exposed to lead at concentrations close to the maximum environmentally relevant level in coastal waters. Additionally, P1 and P2 phagocytes are first shown to have different functions and phenotypes during the response to lead, which indicates the complexity of the phagocytic system in holothurians and contributes to understanding the immunity evolution.

In vivo immunostimulatory effect of the amoebocyte lysate and plasma of Asian horseshoe crab,Tachypleus gigas in a piscine model

Antimicrobial proteins/peptides are becoming a new generation of immunostimulants for prevention and disease control in human and animals,including aquatic animals.As the haemolymph of horseshoe crabs(Tachypleus)contains broad ranges of bioactive compounds,we have explored the in vivo immunostimulating potential of amoebocyte lysate and plasma using a fish model.Indian major carp,Labeo rohita,yearlings were injected intraperitoneally with two doses of lysate and plasma at 50 and 100µg protein per fish.No abnormalities and/or mortalities were recorded in any group.L.rohita injected with 50µg lysate and 100µg plasma protein showed significant enhancement(P<0.01)of various haematological and immunological parameters.There was a significant rise in the total protein and globulin content,myeloperoxidase and respiratory burst activity following injection with 50µg lysate and 100µg plasma protein.The agglutinating and haemagglutinating activities were increased albeit not significantly(P>0.01)in any groups.On the contrary,a significantly high hemolysin titre was recorded in fish that received 100µg plasma protein.Following challenge with Aeromonas hydrophila,both lysate and plasma protein(s)cross protected the fish after 30 days.The highest survival(50%)was recorded in group injected with 50µg lysate protein,followed by 45%in both 100µg lysate and plasma protein injected groups.