A heat-stable blocking factor in the plasma of patients with subacute sclerosing panencephalitis.

The possible role of a defective cell-mediated immune response in the pathogenesis of subacute sclerosing panencephalitis remains unclear. Cell-mediated immunity has been investigated in nine patients with this disorder. In eight patients, a heat-stable blocking factor in the plasma inhibited normal lymphocyte transformation to phytohemagglutinin and mixed lymphocyte cultures. The degree of blocking increased as the disease progressed. The nature of the blocking factor is unknown and is currently under investigation. A heat-stable blocking factor has not been described previously in subacute sclerosing panencephalitis, althouth a heat-labile blocking factor has been reported in a total of five patients.