Mechanisms of immunodepression induced by viruses: possible role of infected macrophages.

Some oncogenic and non-oncogenic viruses induce an immunodepression in their host by decreasing either humoral responses, cellular responses, or both. The mechanism of this immunodepression is still largely unknown, but it is generally agreed that there is a defect in the proliferative potential of lumphocytes in the infected host. Most of the viruses known to induce immunodepression appear to infect host macrophages. Failure of infected macrophages to provide a "proliferation signal" to lymphocytes, and/or destruction of lymphocytes in the lymphoid organs by toxic factors released by infected macrophages could be important mechanisms of immunodepression by viruses.