Related Experiment Video
Updated: Jul 19, 2026
Application of a Mouse Ligated Peyer’s Patch Intestinal Loop Assay to Evaluate Bacterial Uptake by M cells
Published on: December 17, 2011
Mucosal subepithelial binding sites for the bacterial chemotactic peptide, formyl-methionyl-leucyl-phenylalanine
P Anton1, J O'Connell, D O'Connell
1Department of Medicine, National University of Ireland, Cork, Republic of Ireland.
Background:
The bacterial chemotactic peptide N-formyl-methionine-leucine-phenylalanine (FMLP) is produced by enteric flora and is one of the factors implicated in contributing to inflammatory bowel disease. Expression of receptors for FMLP on human phagocytes (polymorphs and monocytes) is well established, but there is conflicting evidence regarding the potential expression of FMLP receptors on other cells within the mucosa, particularly the epithelial cells.
Aims:
To map FMLP receptors within intestinal mucosa using several different experimental approaches.
Methods And Results:
Radioligand binding assays with 'H-FMLP' revealed no specific binding to primary cultured colonic enterocytes or to the cell line HT29, whereas neutrophils, as expected, exhibited specific binding with a Kd of 19 nM and approximately 2 x 10(4) receptors per cell. FITC labelled FMLP exhibited specific, displaceable binding on flow cytometry to neutrophils and monocytes but not to 10 gastrointestinal epithelial cell lines. Isolated lamina propria lymphocytes and peripheral blood lymphocytes exhibited no binding. To confirm the absence of receptors on epithelia, reverse transcription polymerase chain reaction for mRNA for the classic FMLP receptor was performed. While the presence of message was detected in activated peripheral blood phagocytes, it was not detected in epithelial cell lines. To exclude the possibility of FMLP binding to other receptors such as tachykinin receptors on epithelia, FITC labelled FMLP binding in tissue sections confirmed that the binding is subepithelial--that is, in the lamina propria.
Conclusion:
Receptors for FMLP are subepithelial and map to the lamina propria of the gastrointestinal mucosa.
Insights
Receptors for the bacterial peptide N-formyl-methionine-leucine-phenylalanine (FMLP) are not found on intestinal epithelial cells. These FMLP receptors are located in the subepithelial lamina propria of the gastrointestinal mucosa.
Area of Science:
- Gastroenterology
- Immunology
- Cell Biology
Background:
- The bacterial peptide N-formyl-methionine-leucine-phenylalanine (FMLP) is linked to inflammatory bowel disease.
- FMLP receptors are known on human phagocytes, but their presence on intestinal epithelial cells is debated.
Purpose of the Study:
- To precisely map the location of FMLP receptors within the intestinal mucosa.
- To investigate FMLP receptor expression on gastrointestinal epithelial cells.
Main Methods:
- Radioligand binding assays using 'H-FMLP' on colonic enterocytes and HT29 cells.
- Flow cytometry with FITC-labeled FMLP on neutrophils, monocytes, and epithelial cell lines.
- Reverse transcription polymerase chain reaction (RT-PCR) for FMLP receptor mRNA.
- FITC-labeled FMLP binding assays on tissue sections.
Main Results:
- No specific FMLP binding was detected on colonic enterocytes or HT29 cells.
- Neutrophils showed specific binding (Kd 19 nM), while monocytes and lymphocytes did not bind FITC-FMLP.
- RT-PCR confirmed FMLP receptor mRNA in phagocytes but not in epithelial cell lines.
- Tissue section analysis revealed FMLP binding exclusively in the subepithelial lamina propria.
Conclusions:
- FMLP receptors are not expressed on intestinal epithelial cells.
- FMLP receptors are localized to the subepithelial lamina propria in the gastrointestinal mucosa.
Related Concept Videos
01:21Chemotaxis and Direction of Cell Migration
01:25Selectins
01:28Fimbriae, Pili, and Axial Filaments
01:27Chemotaxis in E. coli