Peripheral canine CD4(+)CD8(+) double-positive T cells - unique amongst others

Area of Science:

• Immunology
• Veterinary Medicine
• Cell Biology

Background:

• Double-positive T cells (co-expressing CD4 and CD8) are typically found during T cell development in the thymus.
• Peripheral double-positive T cells with a memory phenotype have been observed in various species, including humans and pigs.
• Recent studies focus on canine peripheral double-positive T cells, revealing unique features.

Purpose of the Study:

• To highlight novel findings on canine peripheral double-positive T cells.
• To compare canine double-positive T cells with their counterparts in other species, particularly pigs and humans.
• To explore the potential roles of canine double-positive T cells in immunity and disease.

Main Methods:

• Comparative analysis of canine, porcine, and human peripheral double-positive T cells.
• Flow cytometry to assess CD4 and CD8 expression levels and subsets.
• Investigation of progenitor cell populations for double-positive T cells.

Main Results:

• Canine CD4(+)CD8(+) T cells are heterogeneous, falling into three distinct subsets based on CD4 and CD8α expression levels.
• Unlike pigs, dogs possess double-positive T cells expressing CD8β, similar to humans.
• Canine CD4(+)CD8(+) T cells can develop from both CD4(+) and CD8(+) single-positive T cells, with CD4(+) being more potent progenitors.
• Canine double-positive T cells display an activated phenotype.

Conclusions:

• Canine peripheral double-positive T cells share more characteristics with human double-positive T cells than with porcine ones due to their heterogeneity and developmental pathways.
• These cells have unique features, including CD8β expression and distinct progenitor relationships.
• Canine double-positive T cells may have significant, yet unrecognized, roles in canine immune responses to infections and inflammatory conditions like autoimmunity, allergy, and cancer.