Toll-like receptors (TLRs) are a family of proteins that play a key role in the innate immune system by recognizing molecular patterns from microbes. They are expressed on immune cells like neutrophils, macrophages, and dendritic cells as well as non-immune cells. Most TLRs are located on the cell surface but TLR9 is intracellular. Stimulation of different TLRs induces distinct patterns of gene expression to activate innate immunity and instruct the development of acquired immunity. The first human TLR was discovered in 1994 and TLRs were shown to induce adaptive immune responses in 1997. TLR signaling involves intracellular adapter proteins and transcription factors that trigger inflammatory responses.

1. TLR
Done by Dr Anees Alsaadi
Nov . 2008

2. What are Toll-like receptors ?
• Are receptors involved in the innate immune
system .
• Recognize specific molecular patterns that are
present in microbial components.

3. Stimulation of different TLRs
induces distinct patterns of
gene expression.
Instructs the
development of Activation of
antigen-specific innate immunity
acquired immunity.

4. Discovery of TLR ?
• Named for their similarity to Toll, a receptor first
identified in the fruit fly Drosophila melanogaster.
• The first reported human Toll-like receptor was
described by Nomura and colleagues in 1994.
• 1997, Charles Janeway and Ruslan Medzhitov
showed that a Toll-like receptor now known as TLR4
could, induce the activation of an adaptive immune
response.

5. Where are TLR receptors found ?
• TLR family members are expressed by:
– Neutrophils.
– Macrophages.
– Dendritic cells.
– Dermal endothelial cells.
– Mucosal epithelial cells.
– TLR2 and TLR4 expressed on B and T cells.

6. Are they intracellular or extracellular?
• Most TLRs are on the cell surface except of
TLR9, which is an intracellular
• In MQ TLR4 expressed on cell surface and is
internalized following engagement of the ligand.
• In TLR4 epithelial cells it resides in the Golgi
apparatus.

7. What are the structure of TLR ?

8. What are the functions of TLR receptors ?
• Engagement of TLRs with their ligands leads
to:
– Pro-inflammatory cytokines,
– Chemokines,
– Effector molecules.
• TLR2 Staphylococcus aureus . Haemophilus
influenzae or with RSV persist longer in the
lungs of TLR4-deficient mice .

9. What are the functions of TLR receptors ?

10. What are the functions of TLR receptors ?

11. How is the signaling in TLR ?

12. How is the signaling in TLR ?

13. How is the signaling in TLR ?

14. How is TLR being regulated ?

15. Thank
you