Human T-cell clones to bee venom phospholipase A2 (PLA), isolated from allergic, hyposensitized and hyperimmune individuals to bee sting, secrete both IL-4 and IFN-gamma after antigen stimulation. However, the production of IL-4 was higher than the production of IFN-gamma. The threshold of the antigen dose required for IL-4 secretion was lower than for IFN-gamma. Furthermore, clones derived from allergic and hyposensitized individuals generally expressed increasing ratios of IL-4/IFN-gamma production with increasing concentrations of PLA. In contrast, most clones isolated from hyperimmune subjects expressed an opposite dose relationship for IL-4/IFN-gamma production.