The Role of the CD8-Positive Subset of T Cells in Proliferative Responses to Soluble Antigens

Using magnetic monosized polymer particles (M 450) coated with a monoclonal mouse IgM anti-CD8 (ITI 5C2) antibody, we were able to selectively remove and isolate functionally active CD8+ T cells from human peripheral blood mononuclear cells. Isolated CD8+ cells did not respond by proliferation to soluble antigens, but proliferated in response to phytohaemagglutinin. However, in the presence of CD4+ T cells, CD8+ cells were able to mount a substantial proliferation when stimulated with soluble antigens. Depletion of CD8+ cells decreased rather than increased the T-cell responses to the antigens glyc-gli, Coxsackie B4, and mumps in healthy individuals. We therefore found no indication of involvement of functionally-active CD8+ suppressor cells in vitro. The T-cell responsiveness to these antigens has previously been shown to be influenced by HLA-DR-associated restriction elements, but the tendency for decreased responsiveness to these antigens by CD8 depletion seemed independent of the DR type of the cell donors. As in healthy subjects, CD8 depletion resulted in a decreased responsiveness to the gluten antigen glyc-gli in untreated and treated coeliac disease patients and to Coxsackie B4 and mumps antigens in Type 1 diabetics.