The cancer-immunity cycle

Question 1

What are two functions of Tregs?

Answer 1

Tregs can inhibit auto-immune responses by preventing the maturation of DCs and priming of T cells. They can also inhibit tumor immunity by directly killing mature DCs with granzymes and so prevent priming of tumor-specific cytotoxic T cells (CTLs).

Question 2

What are the bottlenecks in raising a CTL response against cancer?

Answer 2

1. Central tolerance. The tumour must offer recognizable antigens to make the cancer cell visible to the adaptive immune system (immunogenic).
2. Peripheral tolerance. The tumour must activate DCs to raise a T-cell response. This does not happen.
3. Tumor-associated immunosuppression. CTLs are supressed in the tumor-microenvironment (TME).

Question 3

What are the steps of the Cancer Immunity cycle?

Answer 3

1. Release of cancer cell antigens.
2. Cancer antigen presentation.
3. Priming and activation.
4. Trafficking of T cells to tumors.
5. Infiltration of T cells into tumors.
6. Recognition of cancer cells by T cells.
7. Killing of cancer cells.