Human platelets express CAR with localization at the sites of intercellular interaction

Area of Science:

• Virology
• Immunology
• Hematology

Background:

• Adenoviruses exhibit broad tissue tropism, utilizing the Coxsackie and Adenovirus Receptor (CAR) for cell attachment.
• Platelets are implicated in adenovirus binding, but the presence of CAR on human platelets remains controversial.
• Understanding CAR expression on platelets is crucial for elucidating adenovirus-platelet interactions.

Purpose of the Study:

• To re-investigate and confirm the presence of CAR on human platelets.
• To clarify discrepancies regarding CAR expression on human platelets in prior research.
• To determine the localization and potential regulation of CAR on platelets.

Main Methods:

• Indirect immunofluorescence assays were employed.
• Human platelets were incubated with anti-CAR antibodies (rabbit H-300 polyclonal) and secondary fluorescent antibodies (goat anti-rabbit IgG F(ab')2 Texas Red).
• CAR-positive and negative controls were utilized for validation.

Main Results:

• CAR was confirmed to be expressed on the surface of human platelets.
• CAR expression was observed in a subset of platelets, specifically 3.5 ± 1.9%.
• CAR was also detected within intracellular aggregates at sites of cell-cell contacts, suggesting upregulation upon platelet stimulation.

Conclusions:

• The presence of CAR on human platelets is confirmed, resolving previous conflicting reports.
• CAR expression on platelets is relatively low but may be modulated by platelet activation.
• CAR's localization at intercellular contact sites provides insights into adenovirus-platelet interactions.