Th122 - Mutation of a Single Critical Region in the IgV of Butyrophilin 3 Reveals That One Chain Functions as a Sensor and the Other as a Ligand for the Sensing of Prenyl Pyrophosphates by Vγ2Vδ2 T Cells: Implications for Cancer Immunotherapy

Thursday, June 23, 2022

6:15 PM – 7:30 PM PT

Presenting Author(s)

CM

Craig T. Morita, M.D., Ph.D.

Professor
VA Health Care System/University of Iowa
Iowa City, Iowa, United States

Co-Author(s)

DR

David A. Rhodes, Ph.D.

Postdoctoral Fellow
VA Health Care System/University of Iowa
Iowa City, Iowa, United States
MN

Mohanad H. Nada, Ph.D.

Postdoctoral Fellow
VA Health Care System/University of Iowa
Iowa City, Iowa, United States
YT

Yoshimasa Tanaka, Ph.D.

Professor
Nagasaki University
Nagasaki, Nagasaki, Japan
SS

Shun Sakaraba, Ph.D.

Researcher
Quantum Beam Science Research Directorate
Kyoto, Kyoto, Japan
HW

Hong Wang, M.D., Ph.D.

Research Scientist
VA Health Care System/University of Iowa
Iowa City, Iowa, United States

γδ T cells expressing Vγ2Vδ2 TCRs play critical roles in human immunity to tumors and microbes. These cells use their TCRs for pattern recognition to monitor phosphorylated metabolites in isoprenoid biosynthesis in a process requiring butyrophilin (BTN) 3A1 and BTN2A1. Metabolites are sensed by binding to the intracellular BTN3A1 B30.2 domain. The role played by the extracellular domains (ECD) of BTN3 is unclear. To define this role, ECD residues were mutagenized to alanine and expressed in 293T cells lacking BTN3A1/2/3, and the transfected cells used to stimulate Vγ2Vδ2 T cells. Mutation of 13 IgC and 23 IgV residues on the inner and side faces had no effect. However, 4 residues on the IgV outer face diminished stimulation along with. Others have identified 2 additional residues in this region. Identification of the critical BTN3A ECD region allowed us to investigate the contribution of BTN3A isoforms. Co-expression of wt BTN3A2 or BTN3A3 with wt BTN3A1 results in higher T cell responses due to heterodimerization. Furthermore, expression of wt BTN3A2 or -A3 with IgV-mutant BTN3A1 also results in similar high T cell responses whereas IgV-mutant BTN3A2 with IgV-mutant BTN3A1 does not stimulate. Unexpectedly, IgV-mutant BTN3A2 with wt BTN3A1 decreases stimulation to near background levels. This suggests that wt BTN3A1 protein is expressed with mutant BTN3A2 in a non-functional heterodimer. Thus, in BTN3 dimers, one chain functions as the sensor (using the B30.2 domain) and the other functions as the ligand to activate Vγ2Vδ2 T cells.