Can resting B cells present antigen to T cells?

Area of Science:

• Immunology
• Cell Biology

Background:

• Antigen presentation to T lymphocytes requires antigen-presenting cells (APCs).
• While activated B cells and other APCs like macrophages and dendritic cells are known, resting B cells were not considered capable of antigen presentation.
• Previous studies have not identified resting B cells as APCs.

Purpose of the Study:

• To investigate the potential of resting B cells to present soluble antigens to T cells.
• To identify factors that may have limited the observation of this function in prior research.
• To characterize the T cell responses mediated by resting B cell APCs.

Main Methods:

• Utilizing T cell proliferation and B cell proliferation assays to assess T cell activation.
• Employing varying doses of radiation on resting B cells to determine radiosensitivity of their antigen-presenting function.
• Testing antigen-primed T cells and T cell clones with resting B cells as APCs.

Main Results:

• Resting B cells can present soluble antigens to both T cell clones and antigen-primed T cells.
• The antigen-presenting ability of resting B cells is highly radiosensitive, diminishing significantly at 1500 rads and lost by 3300 rads.
• Two distinct T cell clonal phenotypes were observed: those that proliferate and induce B cell proliferation, and those that only induce B cell proliferation, suggesting separate activation pathways.

Conclusions:

• Resting B cells possess antigen-presenting cell capabilities.
• The radiosensitivity of resting B cells is a key factor explaining their underappreciated role as APCs.
• Distinct T cell activation pathways exist, one leading to T cell proliferation and another to lymphokine release.