Canine neutrophil dysfunction caused by downregulation of beta2-integrin expression without mutation

Area of Science:

• Immunology
• Genetics
• Veterinary Medicine

Background:

• Canine leukocyte adhesion deficiency (CLAD) is characterized by defects in leukocyte integrin CD18, leading to recurrent bacterial infections.
• This condition is primarily observed in Irish setters and is caused by specific genetic mutations.

Observation:

• Two mixed-breed canine littermates presented with symptoms consistent with CLAD, including recurrent pyogenic infections starting at three months of age.
• Neutrophil function tests revealed reduced superoxide production and impaired integrin-mediated adherence and phagocytic activity in the affected dogs.
• Analysis showed a significant decrease in surface expression of CD11b/CD18 and beta2-integrin transcript levels, but without the missense mutations typical of CLAD.

Findings:

• The study identified a novel mechanism for impaired neutrophil function in dogs, involving decreased beta2-integrin transcriptional levels without mutations.
• This downregulation of beta2-integrin led to reduced surface expression, causing defects in adhesion-related neutrophil functions.
• Increased protein expression of NADPH oxidase components (gp91(phox), p47(phox), and p67(phox)) was observed in the affected male dog.

Implications:

• This research expands the understanding of genetic causes for phagocyte dysfunction and recurrent bacterial infections in canines.
• The findings suggest a new diagnostic approach for canine leukocyte adhesion deficiency-like syndromes, focusing on beta2-integrin transcriptional levels.
• Further investigation into this non-mutational defect could reveal new therapeutic targets for immune deficiencies in dogs.