Consequences of secondary or co-infections for immunity

While remarkable progress has been made using genetically altered mice to understand the importance of different cytokines in protecting against experimental infections or co-infections, an examination of the opportunistic infections that occur during HIV infection of humans does not yet show a clear picture of cytokine imbalance. Opportunistic infections appear to result from impairments in cells mediating innate resistance, such as natural killer cells, macrophages, and neutrophils. Some of these defects may not be corrected even if CD4+ T cells were suddenly restored to normal. The lessons from immunodeficient and gene knockout mice now need to be put to the test in the clinic.