When does chronic transplant rejection typically occur?

Chronic transplant rejection is a long-term process that generally occurs more than six months after the transplant procedure. It is characterized by a gradual decline in function of the transplanted organ and is often the result of the immune system's ongoing response to the foreign tissue. This type of rejection can arise due to a combination of cellular and humoral mechanisms and often does not present with immediate symptoms, making it challenging to detect in its early phases.

In contrast, acute rejection usually occurs within the first few days to weeks post-transplant, as the immune system mounts an immediate and aggressive response to what it recognizes as foreign tissue. Identifying the timeline associated with acute versus chronic rejection is crucial for monitoring transplant recipients effectively. Chronic rejection, therefore, is distinguished by its delayed onset and its association with long-term harm to the transplanted organ's function.