Alterations in natural killer and dendritic cell subsets in individuals with HIV-associated neurotuberculosis

One of the commonest HIV-associated opportunistic infections of the central nervous system is neurotuberculosis. Interaction between HIV, Mycobacterium tuberculosis and host immune system in co-infected individuals may result in altered frequencies of immune cells, thereby modulating dissemination and disease progression. We examined the frequencies of natural killer (NK) cell and dendritic cell (DC) subsets in HIV infected individuals with neurotuberculosis (HIVNTB) as compared to individuals with HIV associated systemic TB (HIVSTB), asymptomatic HIV, non-HIV NTB, non-HIV STB, and healthy controls. Peripheral blood mononuclear cells (PBMC) were stained with fluorochrome-conjugated monoclonal antibodies- Lineage cocktail (containing CD3, CD14, CD19, and CD20), HLA-DR, CD16, CD56, CD11c, and CD123, fixed with 2% paraformaldehyde and analyzed on the flow cytometer. The pDCs were significantly reduced in all HIV infected groups, with a marked reduction in HIVNTB cases as compared to healthy controls. While the CD56^- CD16^bt NK cell subset displayed a significant increase in frequency in all three HIV infected groups compared the three HIV negative groups, the CD56^dim CD16^bt subset was significantly lower in frequency in the HIVNTB compared to healthy controls. The decreased frequencies of plasmacytoid DCs and cytotoxic NK cells, which are crucial for innate immune defence against HIV, may result in ineffective virus control and lead to an exacerbated course of disease in HIVNTB individuals.