Final answer:
The statement about T regulatory cells' suppression mechanism is false. Tregs don't necessarily have to bind to the same APC as effector T cells to suppress their function, they can use direct contacts or secrete cytokines to inhibit effector cell activity.
Step-by-step explanation:
The statement that suppression of effector T cells by T regulatory cells is dependent on binding of T reg cell and effector cell on the same APC is false. Regulatory T cells (Tregs) can exert their suppressive function in several ways that do not necessarily require direct concurrent binding to the same APC as the effector T cell. They can modulate the activity of effector T cells via direct cell-cell contact or through the secretion of inhibitory cytokines. In some cases, Tregs can indeed interact with APCs and influence their ability to stimulate effector T cells, but this is not the sole mechanism for suppression.
T regulatory cells express CD4, CD25, and FOXP3 molecules and play a crucial role in maintaining immunological tolerance and preventing autoimmune diseases by suppressing immune responses. It is their unique function to maintain balance in the immune system and prevent excessive or misdirected immune responses.