Toll-like Receptors in Cellular Subsets of Human Tonsil T Cells: Altered Expression During Recurrent Tonsillitis

Respir Res. 2006 Feb 27;7(1):36. doi: 10.1186/1465-9921-7-36.

Abstract

Background: The palatine tonsils have a pivotal role in immunological detection of airborne and ingested antigens like bacteria and viruses. They have recently been demonstrated to express Toll-like receptors (TLRs), known to recognize molecular structures on such microbes and activate innate immune responses. Their activation might also provide a link between innate and adaptive immunity. In the present study, the expression profile of TLR1-TLR10 was characterized in human tonsil T cells, focusing on differences between subsets of CD4+ T helper (Th) cells and CD8+ cytotoxic T lymphocytes (CTL). The study was also designed to compare the TLR expression in T cells from patients with recurrent tonsillitis and tonsillar hyperplasia.

Methods: Tonsils were obtained from children undergoing tonsillectomy, and classified according to the clinical diagnoses and the outcome of tonsillar core culture tests. Two groups were defined; recurrently infected tonsils and hyperplastic tonsils that served as controls. Subsets of T cells were isolated using magnetic beads. The expression of TLR transcripts in purified cells was assessed using quantitative real-time RT-PCR. The corresponding protein expression was investigated using flow cytometry and immunohistochemistry.

Results: T cells expressed a broad repertoire of TLRs, in which TLR1, TLR2, TLR5, TLR9 and TLR10 predominated. Also, a differential expression of TLRs in CD4+ and CD8+ T cells was obtained. TLR1 and TLR9 mRNA was expressed to a greater extent in CD4+ cells, whereas expression of TLR3 mRNA and protein and TLR4 protein was higher in CD8+ cells. CD8+ cells from infected tonsils expressed higher levels of TLR2, TLR3 and TLR5 compared to control. In contrast, CD4+ cells exhibited a down-regulated TLR9 as a consequence of infection.

Conclusion: The present study demonstrates the presence of a broad repertoire of TLRs in T cells, a differential expression in CD4+ and CD8+ cells, along with infection-dependent alterations in TLR expression. Collectively, these results support the idea that TLRs are of importance to adaptive immune cells. It might be that TLRs have a direct role in adaptive immune reactions against infections. Thus, further functional studies of the relevance of TLR stimulation on T cells will be of importance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Infections
  • CD4-Positive T-Lymphocytes / metabolism*
  • CD8-Positive T-Lymphocytes / metabolism*
  • Child
  • Chronic Disease
  • Flow Cytometry
  • Humans
  • Immunohistochemistry
  • Palatine Tonsil / metabolism*
  • Palatine Tonsil / pathology*
  • RNA, Messenger / metabolism
  • Recurrence
  • Reverse Transcriptase Polymerase Chain Reaction
  • Toll-Like Receptors / genetics
  • Toll-Like Receptors / metabolism*
  • Tonsillitis / metabolism*
  • Tonsillitis / microbiology
  • Tonsillitis / pathology

Substances

  • RNA, Messenger
  • Toll-Like Receptors