Tk polyagglutination produced in vitro by an endo-beta-galactosidase

Area of Science:

• Microbiology
• Immunology
• Biochemistry

Background:

• Human red blood cells (RBCs) possess blood group I and i antigens.
• Tk polyagglutination is a rare RBC phenotype associated with altered antigen expression.
• Bacterial enzymes can modify RBC surface antigens.

Purpose of the Study:

• To investigate the enzymatic activity of Bacteroides fragilis culture supernatant on human RBCs.
• To identify the enzymatic basis for Tk-activation.
• To determine the main antigenic determinant of Tk polyagglutinable RBCs.

Main Methods:

• Treatment of human RBCs with Bacteroides fragilis culture supernatant.
• Treatment of human RBCs with purified endo-beta-galactosidase from Escherichia freundii.
• Assessment of RBC agglutinability by BS II lectin.
• Evaluation of blood group I and i antigen activity on treated RBCs.

Main Results:

• Treatment with B. fragilis supernatant or E. freundii endo-beta-galactosidase induced Tk-activation in human RBCs.
• Tk-activated RBCs showed agglutination with BS II lectin.
• Blood group I and i activities were reduced on treated RBCs.
• These findings suggest B. fragilis possesses endo-beta-galactosidase activity.

Conclusions:

• Bacteroides fragilis produces endo-beta-galactosidase activity.
• The primary antigenic determinant of Tk polyagglutinable red cells is a terminal N-acetyl-glucosamine residue.
• This enzymatic activity modifies RBC surface glycans, leading to Tk-activation.