The Molecule That Rebalances Immunity: A New Hope For Lupus Patients

Understanding Autoimmune Imbalance

In healthy people, the immune system recognizes and destroys invading bacteria and viruses while leaving the body’s own tissues unharmed. In autoimmune conditions like lupus, this recognition fails. Specifically, in lupus, rheumatoid arthritis, and type 1 diabetes, this misfiring leads to chronic inflammation that damages the kidneys, skin, joints and other vital tissues.

Today’s lupus treatments—such as B-cell depletion, T-cell blockade, or drugs that block key immune signals—reduce inflammation and slow disease progression by broadly limiting immune activity. While effective, this leaves patients vulnerable to infection, impairs normal immune defense, and increases the risk of complications.

Research has long sought ways to “reset” the immune system rather than shut it down. The discovery of how these two enzymes work together offers a promising new direction toward that goal. PTPN22, identified as a risk gene, plays a central role in this work. It controls how strongly T cells react to signals. This affects whether immune responses are kept in check or go on too long.

The new study, published in Science Advances, centers on two enzymes that act as regulators in the immune system: protein tyrosine phosphatase nonreceptor type 22 (PTPN22) and cluster of differentiation 45 (CD45). PTPN22 is an enzyme that helps regulate the activity of immune cells, while CD45, another enzyme, assists in activating specific types of immune cells. Together, these enzymes form a “push and pull” control system that keeps immune cells from overreacting. When this system breaks down, the body’s defense network can mistakenly turn on itself.

Controlling the Immune Response

Every immune response begins with T cells, a type of white blood cell that detects potential danger through its surface receptors. CD45 helps activate T cells by switching on specific chemical signals within the cell. PTPN22 acts oppositely—it slows down those signals once a threat has been contained.

The new study reveals that the two collaborate in a way that regulates signaling by the T-cell receptor, the sensor that enables cells to recognize threats. In people who inherit a common gene mutation affecting the first enzyme, the system loses its balance. T cells become overly sensitive, reacting even when there’s no threat, and over time, this excessive alertness can trigger chronic autoimmune disease.