Anti-NMDA receptor antibodies are proteins produced by the immune system that mistakenly target and attack the N-methyl-D-aspartate (NMDA) receptors in the brain. These receptors are crucial for communication between nerve cells and play a key role in learning and memory. When these antibodies bind to the receptors, they can disrupt normal brain function. The presence of anti-NMDA receptor antibodies is associated with a rare autoimmune condition known as anti-NMDA receptor encephalitis. This condition can lead to symptoms such as confusion, seizures, and changes in behavior. Early diagnosis and treatment are important for recovery and can involve immunotherapy to reduce antibody levels.