Enhancement of B cell function as antigen-presenting cell during interplay with Th cells

Area of Science:

• Immunology
• Cellular Biology
• T cell-B cell interactions

Background:

• C57BL/6 mouse B cells present antigens (Ag) to T cells, inducing IL-2 secretion but not proliferation.
• Spleen adherent cells act as antigen-presenting cells (APCs), inducing T cell proliferation to OVA.
• The role of B cell stimulation during Ag presentation in T cell response induction was unclear.

Purpose of the Study:

• To investigate if B cells, upon stimulation during Ag presentation, acquire enhanced APC capabilities.
• To determine if stimulated B cells can induce a proliferative Ag-specific T cell response.

Main Methods:

• B cells were cultured with OVA-specific T cell clone 34-7F, with or without prior stimulation.
• Antigen-presenting cell (APC) function was assessed by measuring T cell proliferation and IL-2 receptor (IL-2R) expression.
• Phosphatidyl inositol metabolism and IL-2 mRNA expression in T cells were analyzed.

Main Results:

• Unstimulated B cells proliferated upon culture with T cells and OVA, an effect inhibited by anti-I-Ab mAb.
• Stimulated B cells enhanced phosphatidyl inositol metabolism in T cells upon Ag presentation, unlike unstimulated B cells.
• Stimulated B cells induced IL-2R expression on T cells, leading to IL-2-dependent proliferation, independent of increased IL-2 production by T cells.

Conclusions:

• B cells receive signals from T cells during Ag presentation that enhance their APC function.
• Stimulated B cells can overcome the non-proliferative response of T cells to Ag on unstimulated B cells.
• This study demonstrates a mechanism by which B cells become potent APCs, driving T cell proliferation.