One possible explanation of this difference is that the IFN-γ + IL-2-TNF-α + CD4 T cell subset might convert to monofunctional IFN-γ + and TNF-α + effectors with increasing duration of co-infection (which was shorter in the earlier report): the relationship between S. mansoni and HIV disease is likely to be dynamic as HIV disease progresses. This evidence concerns the gene CD4 and coinfection.