Production of IL-4 and expression of CD40 ligand by human CD8(+) T cells

Background: The role of CD8(+) T cells in IgE synthesis remains unclear. Objective: The aim of this study was to investigate IL-4 production and CD4 0 ligand expression by human CD8+ T cells. Methods: We conducted functional and phenotypic analyses of human T cells in peritoneal washings from sever e combined immunodeficiency mice reconstituted with PBMCs from normal and a topic human donors. We also examined the expression of IL-4 and CD40 ligand by CD8(+) T cells from a patient with adenosine deaminase deficiency who r eceived autologous T cell-directed gene therapy. Results: Transfer of atopic cells into the mice caused production of IgE an d IgG with increased expression of LL-4 and CD40 ligand mRNA. In addition, both intracellular IL-4 and cell surface CD40 ligand were detected in CD8() and in CD4(+) T cells. CD8(+) T-cell lines generated from the patient's T cells carrying the adenosine deaminase gene expressed not only IL-4 mRNA a nd protein but also CD40 ligand mRNA and protein after being stimulated wit h an anti-CD3 mAb. After anti-CD3 stimulation and paraformaldehyde fixation , CD8(+)T cells induced IgE synthesis by normal human B cells in the presen ce of recombinant IL-4. Conclusion: Taken together, these results demonstrate that IL-4-producing a nd CD40 ligand-expressing CD8(+) cells are detectable among human T cells a nd suggest that such cells may promote IgE production by B cells under some conditions.