CD4 and infection: Individuals with low CD4+ T-lymphocyte cellcounts increase the risk of parasitic intestinal infections being opportunistic agents.42 Simultaneous activation of CD4+ T-lymphocyte cells andinterferon-γ (IFN-γ) is required to prevent Cryptosporidium infection.49 CD4+ T-lymphocyte cells are useful for limiting the duration ofdisease, while IFN-γ serves to limit the intensity of the infection.