In vitro cytokine production and growth inhibition of lymphoblastoid cell lines by CD4(+) T cells from Epstein-Barr virus (EBV) seropositive donors

In vitro stimulation of peripheral blood lymphocytes (PBL) from healthy Eps tein-Barr Virus (EBV) seropositive individuals with autologous lymphoblasto id cell lines (LCL) gives rise to CD4(+) and CD8(+) T cells both of which a re cytotoxic for autologous lymphoblastoid cells. Activated EBV-specific CD 4(+) T cells are cytotoxic towards autologous LCL but, paradoxically, CD4() T cells have also been shown to enhance tumour formation in SCID/Hu mice. Here, we show that despite being cytotoxic, CD4(+) T-cell lines from diffe rent donors show considerable variation in their ability to inhibit the lon g-term growth of autologous LCLs in vitro. Following re-stimulation in vitr o with PMA and ionomycin, CD4(+) T cells produced IFN gamma, TNF alpha, TNF beta, IL-2, IL-4, IL-10 and IL-13. TNF alpha, TNF beta and IL-10 productio n were also detected in LCL. IL-6 was only detected in trace amounts in eit her cell type. The ratio of IFN gamma to IL-4 production varied between the CD4(+) T-cell lines, indicating differences in the Th1/Th2 balance of the response. When CD4(+) T cells were re-stimulated using autologous LCL as an tigen-presenting cells, they produced more IL-4 and less IFN gamma or IL-13 when compared with cells re-stimulated by phorbol myristate acetate (PMA) and ionomycin. Using two colour cytokine staining, we showed that many indi vidual CD4(+) T cells produced IFN gamma along with either IL-4 or IL-13. P urified CD4(+) T cells completely inhibited the outgrowth of autologous LCL in five out of nine cases, and partially inhibited outgrowth in the remain ing four. There was no correlation between the pattern of CD4(+) T-cell cyt okine production and the capacity to inhibit outgrowth of autologous LCL. T he killing of LCLs was contact-dependant and not mediated by soluble factor s. We conclude that the ability of CD4(+) T cells to inhibit autologous LCL growth is not directly related to T-helper cell cytokine production, but m ay depend on cytoxicity through surface ligands such as CD95L (FasL) and TN F alpha -related apoptosis-inducing ligand (TRAIL).