Two distinct T cell subsets, CD4⁺ and CD8⁺ CD60 ⁺, and their cytokines are required for in vitro induction of human Ragweed-specific memory IgE responses

CD8⁺CD60⁺ T cells (80-98% CD45RO⁺; 20% CD23⁺) are significantly increased in the blood of serum IgE ⁺ ragweed-sensitized (RS) compared with serum IgE-nonatopic humans (p = 0.001). CD8⁺CD60⁺ T cells of the RS patients produced IL-2, IL-4, IL-10, IL-12, IFN-α. and IFN-γ, but not IL-6 or IL-13. When their PBMC were cultured with ragweed Ag (RA), peak IgE responses occurred on day 10; none was induced with non-cross-reacting or without Ag; nonatopic PBMC did not respond to any stimulant. When either CD4⁺ or CD8 ⁺CD60⁺ T cells were depleted from RS PBMC before culture with RA, no IgE responses were induced. If purified CD4⁺ T cells or low numbers of CD8⁺CD60⁺ T cells were added back to the depleted PBMC, IgE responses were restored. However, higher numbers of CD8 ⁺CD60⁺ T cells totally suppressed IgE responses. Total suppression also was obtained when RS PBMC were cultured with RA and either anti-IL-2, IL-4, IL-10, IL-12, IFN-γ (all concentrations), or IFN-α (low concentrations), but not anti-IL-6 or IL-13. Higher concentrations of anti-IFN-α potentiated IgE responses.