An Underactive Immune System

There are certain conditions, for example an infection by feline immune deficiency virus (FIV) or feline leukemia virus (FeLV), in which the cat's immune system is suppressed.

Affected cats are susceptible to infections and to cancers. Also, every cat that lives into old age is likely to experience a natural decline in the competence of its immune system, and so be subject to an increased incidence of infectious diseases, autoimmune disorders, and cancers.