PLATELETS CONTAIN INTERLEUKIN-1-ALPHA AND INTERLEUKIN-1-BETA WHICH ARE DETECTABLE ON THE CELL-SURFACE AFTER ACTIVATION

Activated platelets have been shown previously to exhibit membrane-bou nd IL-1 bioactivity, which leads to the question of localization of th e cytokine in platelets. Using immunocytological and flow cytometric t echniques, we found IL-1 alpha and IL-1 beta 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 an tibody treatment of platelets revealed the presence of IL-1 (alpha and beta) in low density on the surface of intact cells in contrast to di stinct enrichment in the cytoplasma of damaged platelets. Fibrin fibre s present between cells indicated adsorbance of IL-1. There was also w eak binding of anti-IL-1 alpha to the surface of thrombin-activated pl atelets 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 prese nce of both IL-1 alpha and IL-1 beta in resting and activated platelet s without being able to demonstrate localization of the cytokines to s pecific subcellular structures.