T-lymphocytes have a protein, PD-1, on their surface. Some cancer cells have a receptor molecule on their surface which binds with PD-1, inactivating the T-lymphocyte.

A monoclonal antibody, lambrolizumab, has been produced against this receptor.

Trials showed that in 54 of 135 people with advanced skin cancer who were given lambrolizumab the tumours more than halved in volume. In six of the 57 people who were given the highest dose the tumours disappeared.

What may be correctly concluded from this information?

1. Lambrolizumab binds with a receptor on the surface of skin cancer cells.

2. Cancer cells to which lambrolizumab is bound cannot inactivate T-lymphocytes.

3. Lambrolizumab targets and kills skin cancer cells.

4. Lambrolizumab allows a patient’s own immune system to kill cancer cells.