Study Design.
Human arachnoid cells were examined immunohistochemically for expression of HLA-DR or Fc receptors.
Objective.
To assess the ability of arachnoid cells to express HLA-DR and act as antigen presenting cells.
Summary of Background Data.
An intradural inflammatory reaction surrounds the cervical nerve roots and radicular vessels in patients with spondylotic cervical myeloradiculopathy. Active arachnoid proliferation and fibrosis in this reaction suggest these cells are actively involved in this inflammatory process. An inflammatory response is initiated by an antigen presenting cell. Evidence suggests that arachnoid cells may be antigen presenting cells, like macrophages, because they can phagocytize foreign tissue and have immunoglobulin G and complement receptors.
Methods.
Spinal arachnoid obtained from patients undergoing spinal surgery for intramedullary processes was grown in culture. The arachnoid cells were characterized and examined immuohistochemically for the expression of HLA-DR and Fc receptors.
Results.
HLA-DR was expressed in vivo and in vitro by arachnoid cells. The macrophage Fc receptor was not expressed in vivo nor in vitro by arachnoid cells.
Conclusion.
Finding in vivo and in vitro HLA-DR expression on arachnoid cells adds further support to the concept that arachnoid cells have the potential to serve as antigen presenting cells. The absence of Fc receptors, although necessary for macrophages, does not negate antigen presenting function because other types of cells—e.g., endothelium—can present antigen without displaying Fc receptors. These experiments provide new evidence that arachnoid cells may initiate or sustain the intradural inflammatory reaction found in cervical myeloradiculopathy.
