A CD22-Shp1 phosphatase axis controls integrin β₇ display and B cell function in mucosal immunity

Area of Science:

• Immunology
• Cell Biology

Background:

• Integrin α4β7 is critical for lymphocyte trafficking to the gut and gut-associated lymphoid tissue (GALT).
• Regulation of α4β7 surface expression is key to maintaining intestinal immunity.

Purpose of the Study:

• To investigate the roles of tyrosine phosphatase Shp1 and B cell lectin CD22 in regulating α4β7 surface expression.
• To elucidate the mechanisms by which Shp1 and CD22 influence gut immunity.

Main Methods:

• Investigated the interaction between Shp1, CD22, and integrin β7.
• Assessed the impact of Shp1 activity and CD22 expression on β7 endocytosis and phosphorylation.
• Analyzed lymphocyte homing to GALT and intestinal immune responses in genetically modified B cells.

Main Results:

• Shp1 inhibits β7 endocytosis, increasing surface α4β7 and lymphocyte homing to GALT.
• CD22 binds β7 in a sialic acid-dependent manner, recruiting Shp1 to restrain β7 phosphorylation and endocytosis.
• Reduced Shp1 activity or CD22 deficiency led to decreased surface α4β7 and impaired homing to GALT.
• CD22 deficiency selectively impaired intestinal antibody and pathogen responses.

Conclusions:

• Shp1 and CD22 are novel regulators of α4β7 surface expression and function.
• This pathway is essential for effective lymphocyte homing to the gut and intestinal immunity.
• Targeting Shp1 or CD22 may offer therapeutic strategies for modulating gut immunity.