# TLR2-induced surface mobilization and release of CD14 in human platelets

## TL;DR

Human platelets contain CD14 molecules that move to the surface and release when TLR2 is activated, linking platelet function to immune responses.

## Contribution

This study reveals that CD14 in platelets is mobilized and released upon TLR2 stimulation, expanding the role of platelets in immune signaling.

## Key findings

- CD14 is detectable on the surface of platelets after TLR2 or collagen stimulation, but not in resting or TLR4-stimulated platelets.
- TLR2 activation leads to the release of soluble CD14 (sCD14) from platelets.
- CD14 co-localizes with TLR2 and TLR4 in platelets and shows distinct distribution patterns upon stimulation.

## Abstract

In addition to hemostasis, platelets are involved in immunological processes and express toll-like receptors (TLR) like TLR2 and TLR4. Since CD14 represents an essential co-receptor for TLR in immune cells, this study investigated the presence, the release and the distribution of CD14 in human platelets. Washed human platelets (WP) were used for analysis, either unstimulated or stimulated with the TLR2 agonist Pam3CSK4 or with the TLR4 agonist LPS (lipopolysaccharides from Escherichia coli). CD14 expression was detected by flow cytometry, soluble CD14 (sCD14) by an immunoassay. The platelet content of CD14 was measured with Western Blot analysis. Visualization of CD14 was performed with transmission electron microscopy or high-resolution fluorescence microscopy. CD14 expression was detectable after TLR2- or collagen-induced stimulation, but not in resting and TLR4-stimulated platelets. TLR2 activation induced the release of sCD14. In adherent non-permeabilized WP, CD14 expression was found locally condensed in the central region. In permeabilized platelets, an intracellular CD14-specific thread-like staining was visible predominantly along the membrane. CD14 showed a distribution pattern in co-localization with TLR2 and TLR4. In conclusion, platelets contain CD14 molecules co-localized with TLR2 and TLR4, which can be recruited to the surface after specific platelet stimulation and released as sCD14.

The online version contains supplementary material available at 10.1038/s41598-025-22715-7.