Innate lymphoid cells (ILCs) type 3, also known as lymphoid tissue inducer cells, plays a major role in both the development and remodeling of organized lymphoid tissues and the maintenance of adaptive immune responses. HIV/simian immunodeficiency virus (SIV) infection causes breakdown of intestinal barriers resulting in microbial translocation, leading to systemic immune activation and disease progression. However, the effects of HIV/SIV infection on ILC3 are unknown. Here, we analyzed ILC3 from mucosal and systemic lymphoid tissues in chronically SIV-infected macaques and uninfected controls. ILC3 cells were defined and identified in macaque lymphoid tissues as non-T, non-B (lineage-negative), c-Kit(+)IL-7R alpha(+) (CD117(+)CD127(+)) cells. These ILC3 cells highly expressed CD90 (similar to 63) and aryl hydrocarbon receptor and produced IL-17 (similar to 63), IL-22 (similar to 36), and TNF-alpha (similar to 72) but did not coexpress CD4 or NK cell markers. The intestinal ILC3 cell loss correlated with the reduction of total CD4(+) T cells and T helper (T-h) 17 and Th22 cells in the gut during SIV infection (P < 0.001). Notably, ILC3 could be induced to undergo apoptosis by microbial products through the TLR2 (lipoteichoic acid) and/or TLR4 (LPS) pathway. These findings indicated that persistent microbial translocation may result in loss of ILC3 in lymphoid tissues in SIV-infected macaques, further contributing to the HIV-induced impairment of gut-associated lymphoid tissue structure and function, especially in mucosal tissues.
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