Analysis of CD3 antigen expression in patients with ataxia-telangiectasia.

The expression of CD3 molecules by the lymphocytes of five patients with ataxia-telangiectasia was examined using the murine monoclonal antibody OKT3. By immunofluorescent staining, fewer of the patients' peripheral blood mononuclear cells and purified T cells expressed CD3 compared with normals. The proliferative response of the patients' cells to OKT3 was also less than normal. However, the mononuclear cells from all five patients produced IL-2 after OKT3 stimulation; in four patients IL-2 was normal, while one patient produced greater than normal levels. While the expression of cellular IL-2 receptors and the release of these receptors into culture supernatants was generally less in ataxia-telangiectasia patients, the levels of receptor expression were not significantly less than normal. As analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis, the CD3 molecules from ataxia-telangiectasia patients' lymphocytes were no different from those of normal individuals. These results suggest that patients with ataxia-telangiectasia have structurally normal CD3 molecules which may be used to activate cells normally for some but not all T cell functions.