Interferons are released by some macrophages and lymphocytes, but also by cells carrying what pathogen?

Answer;
Interferons are released by some macrophages and lymphocytes, but also by cells carrying viruses.

Explanation; 
Interferons are proteins called cytokines that are produced by the white blood cells, fibroblasts, macrophages or T-cells as part of the immune response to a viral infection or other immune triggers. These proteins have the ability to interfere with the production of new virus particles, thus the name interferons.