Cutting Edge: Redundant Roles for MHC Class II-, CD1d-, and MR1-restricted T Cells in Clearing Bartonella Infection

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• The role of unconventional T cells in systemic bacterial infections is not well understood.
• Mucosal immunity relies heavily on these T cells, but their systemic function is less defined.

Purpose of the Study:

• To investigate the role of various T cell subsets in controlling systemic Bartonella infection in mice.
• To determine how different T cell populations, including unconventional T cells, contribute to bacterial clearance and antibody production.

Main Methods:

• Utilized mouse models deficient in specific T cell subsets (MHC class I, MHC class II, CD1d, MR1).
• Infected mice with Bartonella taylorii to establish persistent bacteremia.
• Monitored bacterial clearance kinetics and antibody production in different knockout mouse models.

Main Results:

• Alpha-beta T cells were essential for antibody production and clearance of Bartonella taylorii.
• Mice deficient in MHC class I, MHC class II, CD1d, or MR1 individually cleared the infection normally.
• Combined deficiency in MHC class II and CD1d or MHC II and MR1 impaired bacterial clearance, suggesting compensatory roles.

Conclusions:

• Unconventional T cells (CD1d- and MR1-restricted) can compensate for the absence of MHC class II-restricted T cells in controlling systemic bacterial infections.
• These T cells play a significant, previously underappreciated role in systemic bacterial infection control, likely by assisting in antibody production.