Antigen-presenting human B cells are expanded in inflammatory conditions

Area of Science:

• Immunology
• Cell Biology

Background:

• B cells traditionally known for antibody production.
• Emerging evidence highlights diverse B cell immunologic functions.
• Antigen presentation by B cells to activate T cells is a key area of interest.

Purpose of the Study:

• To identify and characterize a phenotypically defined human B cell subset with antigen-presenting and T cell-stimulatory properties.
• To investigate the potential role of this B cell subset in inflammatory diseases.

Main Methods:

• Phenotypic characterization of B cells using flow cytometry, focusing on CD21 and CD86 expression.
• Assessment of T cell-stimulatory activity using autologous mixed-lymphocyte reactions.
• Analysis of B cell subset expansion in peripheral blood from vaccinated individuals and patients with rheumatoid arthritis.

Main Results:

• Identification of a human B cell subset (CD21^lowCD86^pos B_APC) with strong T cell-stimulatory capacity.
• These B_APC cells are phenotypically characterized as CD27⁺ class-switched IgM^negIgD^neg lymphocytes.
• Expansion of the B_APC subset was observed post-vaccination and in patients with rheumatoid arthritis, indicating a role in inflammation.

Conclusions:

• The identified B_APC subset possesses potent immunostimulatory properties.
• This subset exhibits migratory potential towards inflammatory sites.
• B_APC cells represent a promising therapeutic target for inflammatory diseases.