Platelets Contain Interleukin‐1 Alpha and Beta which are Detectable on the Cell Surface After Activation

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Abstract
Activated platelets have been shown previously to exhibit membrane-bound IL-1 bioactivity, which leads to the question of localization of the cytokine in platelets. Using immunocytological and flow cytometric techniques, we found IL-la and IL-Iβ in the cytoplasma of both resting and thrombin-activated platelets. Immunogold-silver staining of the cell surface of activated platelets as well as pre-embedding antibody treatment of platelets revealed the presence of IL-1 (α and β) in low density on the surface of intact cells in contrast to distinct enrichment in the cytoplasma of damaged platelets. Fibrin fibres present between cells indicated adsorbance of IL-1. There was also weak binding of anti-IL-1α to the surface of thrombin-activated platelets as shown by flow cytometry. Following activation there appears to be some transfer of IL-1 onto the cell surface of activated cells, the bulk of the cytokine, however, is probably not released prior to platelet disintegration. In summary, we present evidence for the presence of both IL-1α and IL-1β in resting and activated platelets without being able to demonstrate localization of the cytokines to specific subcellular structures.