Questions: Chemical signals produced by and T cells called interleukins can activate B cells.

The answer is: macrophages and T cells.

Explanation:

• Interleukins are a group of cytokines that are produced by a variety of cells, primarily by immune cells.
• Macrophages are a type of white blood cell that engulfs and digests cellular debris and pathogens. They are known to produce interleukins as part of the immune response.
• T cells, another type of white blood cell, also produce interleukins. These cells play a crucial role in the immune system by helping to activate other immune cells, including B cells.
• B cells are responsible for producing antibodies, and their activation is a key step in the adaptive immune response.

In summary, macrophages and T cells produce interleukins, which can activate B cells.