Gram-positive bacterial cell wall products upregulate surface expression of intercellular adhesion molecule 1, human leucocyte antigen DR and CD14 on monocytes in human whole blood

Abstract

Abstract Background The aim was to investigate the influence of Gram-positive cell wall components on monocyte surface inflammatory receptors compared with lipopolysaccharide (LPS) in human whole blood. Methods Human whole blood from six healthy donors was incubated with peptidoglycan (PepG) 10 μg ml−1 from Staphylococcus aureus and Bacillus subtilis, lipoteichoic acid (LTA) 100 μg ml−1 from S. aureus and LPS 10 ng ml−1 from Escherichia coli in microcentrifuge tubes at 37°C with slow rotation for 4 h. Subsequent to incubation with fluorescein isothiocyanate (FITC)- and phycoerythrine (PE)-labelled monoclonal antibodies, surface molecule (CD14, CD54, CD58, CD64, CD80 and human leucocyte antigen (HLA) DR) expression was analysed by flow cytometry performed on the FACScan using the CellQuest software. Results All surface molecules except CD80 were expressed constitutively on monocytes in whole blood. Stimulation with either type of PepG, LTA and LPS did not induce any changes in expression of CD58 or CD64, nor did they induce expression of CD80. However, significant upregulation of CD54 and HLA-DR was observed in all donors. Contrary to LPS, PepG and LTA also upregulated the expression of monocyte surface CD14. Conclusion The Gram-positive cell wall products PepG and LTA strongly upregulated the expression of intercellular adhesion molecule 1 (CD54) and HLA-DR on monocytes in human whole blood, as was seen in LPS-stimulated whole blood. In contrast to Gram-negative endotoxin, the Gram-positive cell wall products also upregulated the expression of the LPS receptor CD14. This suggests possible differences in intracellular signalling between Gram-positive cell wall products and Gram-negative LPS in monocytes.