Cells with natural killer activity in human rabies

Cytotoxic lymphocyte function in 13 patients with rabies was studied by counting the number of CD56 cells and assessing natural killer (NK) cell activity. There was no significant difference in the number of killer cells between rabies patients and 31 normal controls (P greater than 0.05). Two of six non-fatal encephalitic patients due to causes other than rabies had reduced CD56 numbers. Base-line NK cell responses versus K562 cell targets did not differ among the normal control and rabies groups (P greater than 0.05). Study of the non-rabies encephalitis group showed heterogeneous results with wide variation. Significant enhancement of NK activity was seen in four rabies patients and in 10 normal control subjects tested after interferon-alpha (IFN-alpha) and IL-2. None of the four patients with encephalitis due to causes other than rabies showed such enhancement. Our results suggest that NK cells of rabies patients are not fully stimulated and that this might contribute to the virulence of rabies. The cause of this phenomenon remains unknown.