The clonal Th2 cells are highly prone to undergo spontaneous apoptosis.

Purified CD3⁺CD4⁺CD45RO⁺ cells from healthy individuals (♦) and CD3⁻CD4⁺ cells from hypereosinophilic patient 1 (●) and patient 2 (▪) were cultured in the absence of exogenous cytokine. Cells were recovered after 24, 48, 72, and 96 hours of culture. Apoptotic cells were detected by flow cytometry according to FSC/SSC parameters. Results are the means ± SEM of percent apoptotic cells of 5 experiments). *P < .005 as compared with control CD3⁺CD4⁺CD45RO⁺ cells from healthy individuals (ANOVA test).