Which immune cells primarily lower the activity of other leukocytes?

Regulatory T cells, also known as Tregs, play a crucial role in maintaining immune system homeostasis by suppressing the activity of other leukocytes. These cells help prevent excessive immune responses that can lead to tissue damage and autoimmune diseases. They achieve this through a variety of mechanisms, such as the secretion of anti-inflammatory cytokines, direct cell-to-cell interactions, and modulation of dendritic cells.

The unique function of regulatory T cells is essential for downregulating immune responses after an infection has been cleared, or in situations where the immune response needs to be controlled to prevent harmful overreactions. This suppression is vital for preventing autoimmune conditions, where the immune system mistakenly attacks the body’s own tissues.

Other immune cell types, such as B lymphocytes and helper T cells, primarily facilitate or enhance immune responses rather than suppress them. Cytotoxic T cells are involved in directly killing infected or cancerous cells but do not have a role in dampening other immune cells' activity.