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Insights Into Cetacean Immunology: Do Ecological and Biological Factors Make the Difference?
Letizia Marsili1, Giovanni Di Guardo2, Sandro Mazzariol3
1Department of Physical, Earth and Environmental Sciences, University of Siena, Siena, Italy.
Insights
This study investigated Major histocompatibility complex (MHC) class I chain-related protein A (MICA) in cetaceans, finding its expression linked to environmental contaminants and proposing MICA as a non-invasive stress marker in skin biopsies.
Area of Science:
- Marine Mammal Immunology
- Environmental Toxicology
- Molecular Biology
Background:
- Major histocompatibility complex (MHC) class I chain-related protein A (MICA) plays a role in immune responses.
- Cetaceans face environmental stressors, necessitating biomarkers for health assessment.
- Understanding MICA expression in cetaceans can reveal immune system responses to contaminants.
Purpose of the Study:
- To evaluate MICA expression in cetacean fibroblast cell cultures.
- To identify variations in MICA expression related to ecological and biological factors.
- To investigate MICA expression changes following in vitro exposure to various contaminants.
Main Methods:
- Immunofluorescence technique applied to fibroblast cell cultures from cetacean skin biopsies.
- Sampling of free-ranging and stranded cetaceans from the Sea of Cortez and Mediterranean Sea.
- In vitro exposure of cell cultures to organochlorines, flame retardants, PAHs, MeHg, and BPA.
Main Results:
- Cetaceans from the Sea of Cortez exhibited higher basal MICA activity and lower organochlorine levels compared to Mediterranean species.
- A negative correlation (r = -0.45) was observed between high MICA levels and low total organochlorine concentrations.
- In vitro contaminant exposure predominantly upregulated MICA protein expression, with some species-specific downregulation observed.
Conclusions:
- MICA expression alterations in cetaceans indicate organismal stress and modified immune responses.
- MICA is a potential non-invasive immunological marker for cetacean health assessment.
- Skin biopsy analysis of MICA offers a viable alternative to blood-based immunological measurements.
Abstract:
The aim of this study was to evaluate the expression of Major histocompatibility complex (MHC) class I chain-related protein A (MICA) in fibroblast cell cultures of cetaceans (skin biopsies of free-ranging specimens and skin samples of freshly stranded cetaceans) by an immunofluorescence technique and to outline possible variations in MICA expression linked to different ecological and biological factors, while also investigating MICA expression after in vitro treatments with different contaminants. Free-ranging or stranded specimens of cetaceans were sampled in the Sea of Cortez (Mexico) (Balaenoptera edeni, Delphinus capensis, and Orcinus orca) and in the Mediterranean Sea (Balaenoptera physalus, Physeter macrocephalus, Tursiops truncatus, and Stenella coeruleoalba). Cell cultures were treated with an OC mixture, flame retardants, PAHs, MeHg, and BPA. The three species from the Sea of Cortez showed higher basal activity of MICA and lower levels of DDTs and PCBs than the Mediterranean species. A Pearson's linear coefficient equal to -0.45 also confirmed this tendency to have high levels of MICA and low total OC levels. Treatment of cultured fibroblasts with different contaminants mostly resulted in the upregulation of MICA protein expression by at least one treatment dose; downregulation was also found in some species or treatments. MICA alteration indicates a state of stress of the organism and a modification of the immune system's response and can be proposed as a non-invasive immunological marker that can be measured in skin biopsy samples, thus offering a good alternative to blood measurements.
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