Regulatory function of the Th2 clones in vivo. The DTH response in LEW rats was elicited in animals injected with Th1 TCR Vβ9, irradiated Th2 TCR Vβ9 cell clones and irradiated naive LEW T cells in a 1:1 ratio. Bars represent the mean ± SD Δ ear thickness (inches × 10–2,