Related Experiment Videos
Induction of target cell apoptosis by channel catfish cytotoxic cells
R J Hogan1, W R Taylor, M A Cuchens
1Department of Microbiology, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA.
Abstract:
This study examines cytotoxic mechanisms used by channel catfish peripheral blood-derived effector cells. Transmission electron microscopy (TEM), coupled with [(3)H]thymidine DNA fragmentation (JAM) and terminal deoxynucleotidyl nick-end labeling (TUNEL) assays, provided the first evidence that catfish peripheral blood cytotoxic effectors killed allogeneic targets via an apoptotic pathway. TEM demonstrated that the effector cell population present within peripheral blood leukocytes (PBLs) was composed of agranular lymphocytes that formed conjugates with, and induced apoptosis in, allogeneic target cells. Both JAM and TUNEL assays showed that PBLs induced target cell DNA fragmentation within 1 h of coculture. In addition, fixed effectors did not induce target cell necrosis or apoptosis, and target cell lysis was completely inhibited by chelation of free Ca(2+) by EGTA. These results suggest that catfish peripheral blood-derived effector cells utilize a secretory mechanism rather than a ligand-based mechanism to trigger apoptosis.
Insights
Channel catfish effector cells induce target cell apoptosis via a secretory mechanism, not direct cell contact. This research reveals novel cytotoxic pathways in fish immunity.
Area of Science:
- Immunology
- Cell Biology
- Aquatic Animal Health
Background:
- Peripheral blood leukocytes (PBLs) in channel catfish possess cytotoxic capabilities.
- Understanding fish immune mechanisms is crucial for aquaculture and comparative immunology.
Purpose of the Study:
- To elucidate the cytotoxic mechanisms employed by channel catfish peripheral blood-derived effector cells.
- To determine if catfish effector cells induce apoptosis or necrosis in target cells.
Main Methods:
- Transmission electron microscopy (TEM) for ultrastructural analysis.
- [(3)H]thymidine DNA fragmentation (JAM) and TUNEL assays to detect DNA fragmentation.
- Coculture experiments with allogeneic target cells and calcium chelation (EGTA).
Main Results:
- Catfish PBLs, specifically agranular lymphocytes, induced apoptosis in allogeneic target cells.
- DNA fragmentation was observed within 1 hour of coculture, confirmed by JAM and TUNEL assays.
- Cell lysis was inhibited by calcium chelation, and fixed effectors did not induce cell death, suggesting a secretory mechanism.
Conclusions:
- Channel catfish peripheral blood effector cells trigger target cell apoptosis through a secretory mechanism.
- The mechanism appears to involve the release of cytotoxic factors rather than direct cell-surface ligand interactions.
- This study provides the first evidence of an apoptotic pathway utilized by catfish peripheral blood cytotoxic effectors.