CSF neopterin concentrations in the 73 subjects with CNS opportunistic diseases (OIs) included 16 with progressive multifocal leukoencephalopathy (PML), 13 with cytomegalovirus encephalitis (CMV-E), 18 with toxoplasmic encephalitis (toxo), 16 with cryptococcal meningitis (crypto) and 10 with primary CNS lymphoma (PCNSL), and for comparison, neuroasymptomatic HIV positive (NA) subjects with <200 blood CD4 counts (collapsed from two groups in Figure 2) and ADC 1-4 (also collapsed from two groups in Figure 2). The box and whiskers and statistical methods are as described for Figure 2. The CSF neopterin in the PML group differed from the CMV-E (P < 0.001) and ADC 1-4 group (P < 0.01) but not from the other OI groups or from the NA group. The CMV encephalitis patients had the highest levels and in addition to differing from the PML group, differed from the toxoplasmosis patients (P < 0.01) and neuroasymptomatics (P < 0.001), but not the ADC group. The toxoplasmosis group, in addition to differing from the CMV group also differed from the ADC group (P < 0.05) but not the other OIs or NAs. The cryptococcal meningitis group differed from the NA with low CD4 T cells/μl (P < 0.05) while the PCNSL group did not differ from the other groups.