Adaptive Immunity

What is the adaptive immune system?

A specific defense that targets particular pathogens and creates immune memory.

What triggers the adaptive immune response?

Antigens presented by antigen-presenting cells (APCs).

What are the two main branches of adaptive immunity?

Humoral (B cells/antibodies) and cell-mediated (T cells).

What happens first when a pathogen enters the body?

An antigen-presenting cell (like a macrophage) engulfs the pathogen.

What does the antigen-presenting cell do next?

Displays the antigen on its surface using MHC II.

What cell recognizes the antigen on the APC?

Helper T cell (CD4+).

What happens when the helper T cell is activated?

It releases cytokines that activate B cells and cytotoxic T cells.

What do activated B cells do?

Differentiate into plasma cells that produce antibodies.

What do antibodies do?

Bind to antigens, neutralize toxins, and mark pathogens for destruction.

What do cytotoxic T cells (CD8+) do?

Destroy infected or abnormal (cancer) cells.

What is the role of helper T cells in adaptive immunity?

They coordinate the immune response by activating other immune cells.

What are memory cells?

Long-lived B and T cells that provide faster responses to future infections.

What happens after the pathogen is eliminated?

Regulatory T cells (Tregs) are activated to calm down the immune response.

What do regulatory T cells (Tregs) release to suppress other cells?

Inhibitory cytokines such as IL-10 and TGF-β.

What is the main role of regulatory T cells?

To prevent overreaction and autoimmune responses by stopping excess immune activity.

What happens after Tregs suppress the immune response?

The immune system returns to homeostasis (balance).

How does adaptive immunity differ from innate immunity?

It is slower at first, specific to pathogens, and has memory.

What is the secondary immune response?

A faster, stronger response upon re-exposure to the same pathogen due to memory cells.