α2-Macroglobulin-Kallikrein Potentiates Contact System Activity: Possible Effect in Asthma

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Abstract
Bradykinin release, an end product of contact system activation, is thought to play a significant role in the pathophysiology of asthma. We have found an increased level of native α2-macroglobulin-kallikrein (α2M-KK) in asthma plasmas, and have demonstrated increased levels of contact system activity in these plasmas under certain laboratory conditions. We investigated the possible role of α2M-KK as a modulator of the contact system activity. α2M-KK potentiated the factor XII activation on kaolin and the kallikrein production in a dextran-sulfate-mediated assay. This potentiation presumably involves a proteolytic effect of α2M-KK on high molecular weight kininogen.