B7-dependent T-cell costimulation in mice lacking CD28 and CTLA4.

Area of Science:

• Immunology
• Molecular Biology
• Cellular Biology

Background:

• T-cell activation requires costimulatory signals, primarily mediated by CD28 and CTLA4 interacting with B7 molecules.
• The precise mechanisms and receptors involved in B7-mediated costimulation are not fully elucidated.

Purpose of the Study:

• To determine if a T-cell molecule, distinct from CD28 and CTLA4, mediates B7 costimulation.
• To investigate the role of this potential novel receptor in T-cell activation and immune responses.

Main Methods:

• Generation of mice lacking both CD28 and CTLA4 (CD28/CTLA4(-/-)).
• Assessment of T-cell activation markers and proliferation in vitro and in vivo.
• Functional assays using B7-transfected cells and CTLA4-Ig blockade.
• Evaluation of cardiac allograft survival in CD28/CTLA4(-/-) recipients.

Main Results:

• CD28/CTLA4(-/-) mice exhibited reduced T-cell activation and proliferation, similar to CD28(-/-) mice.
• B7-dependent costimulation was confirmed in CD28/CTLA4(-/-) T cells.
• T-cell proliferation was inhibited by CTLA4-Ig and B7-deficient antigen-presenting cells, but enhanced by B7-expressing cells.
• CTLA4-Ig treatment prolonged cardiac allograft survival in CD28/CTLA4(-/-) mice.

Conclusions:

• The findings strongly suggest the existence of an additional T-cell receptor for B7 molecules.
• This novel receptor plays a role in T-cell costimulation and immune regulation.
• The study opens new avenues for understanding T-cell signaling and developing immunotherapies.