Tonsils may be a transmission site for the spread of HIV, say researchers in an article in the August issue of The American Journal of Pathology.
Scientists have questioned whether HIV transmission is facilitated by the tonsils, which contain high numbers of immune cells that may be easily accessible to HIV.
Researchers led by Sharon M. Wahl, PhD, of the National Institute of Dental and Craniofacial Research, National Institutes of Health, compared the gene expression profiles of tonsils and oral gingiva. Although many of the genes they examined had similar expression patterns, they observed differences between those from the tonsils and those from the gingivae. They found that several genes related to immune functions had significantly higher expression in the tonsils, while keratin genes, which "thicken" the tissue and provide barrier protection, were expressed more strongly in the gingivae.
Researchers also found that while HIV coreceptor CXCR4 protein was expressed in gingivae, oral mucosa and tonsils, it was expressed the strongest in the tonsils. The levels of other molecules that may bind and entrap HIV also were higher in the tonsils. However, when researchers examined antiviral proteins, they found lower levels of secretory leukocyte protease inhibitor, defensins and thrombospondin in the tonsils.
Researchers concluded that the decreased amount of keratin and antiviral proteins in the tonsils makes the tonsils more permeable to foreign invaders, thus allowing the tonsils to function in immune surveillance. However, it also makes the site more accessible to pathogens that infect immune cells. Future studies are needed to clarify how host vulnerability is influenced by the tonsils during exposure to HIV.
