Soluble antigen induces T lymphocytes to secrete an endoglycosidase that degrades the heparan sulfate moiety of subendothelial extracellular matrix

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Abstract
The antigen‐mediated induction of heparanase, an endoglycosidase capable of degrading heparan sulfate from the subendothelial extracellular matrix (ECM), was investigated in a rat T lymphocyte cell line reactive against the basic protein (BP) of myelin. We found that nonactivated T lymphocytes could be induced to express heparanase activity following exposure to soluble but not to ECM‐bound BP. The induction of heparanase was immunologically specific and indpendent of the presence of syngeneic or allogeneic antigen presenting cells (APC). However, anti‐IA antibodies inhibited heparanase expression. Soluble BP induced secretion of heparanase into the culture medium within minutes, despite inhibition of protein synthesis. Cell lysates of T lymphocytes contained heparanase activity. Thus, T lymphocytes secrete a preformed heparanase following exposure to specific antigen.