| A cytokine. Inteferons are a large group of proteins that elicit a virus-unspecific antiviral activity. That is to say, when released into the bloodstream, they interact with other cells and help them prepare for a wide spectrum of viral attack. The interferon binds to specific cell surface receptors which then cause gene activation of antiviral systems. They can also kill tumor cells through antiproliferative mechanisms. Finally they can often interact with the immune system to modulate infection response.
Antiviral activity
The inhibition of viral DNA replication, which is necessary for the virus to multiply inside the cell before breaking the cell open (lysogenesis) and infecting neighboring cells.
Antiproliferative activity
There are several ways that interferon can affect tumor cells, either by cytostatic (stopping cell growth) or cytotoxic (killing cells) mechanisms:
Interferon can sometimes even cause a reversion in the malignant cells, bringing them back to normal.
Immunomodulatory activity
- induction of expression of other cytokines
- activation of macrophages, which digest infected cells
- activation of lymphocytes
- modulation of tumor-associated antigen expression
Inteferons are clinically very interesting because of their antiviral and growth-inhibition potential. | 
