To evaluate cell-mediated immune responsiveness to pollen allergens in atopic subjects, we studied the deoxyribonucleic acid (DNA) synthetic responses of their cultured lymphocytes to purified ragweek antigens E, K, and Ra-3. Since lymphocytes from some highly ragweed-sensitive subjects gave poor proliferative responses when harvested on day 6, we undertook a series of dose-response and time-course studies in atopic and control subjects. Surprisingly, vigorous DNA synthetic responses to antigen E occurred with lymphocytes from all 45 subjects, including 19 highly ragweed-sensitive atopic and control subjects. Surprisingly, vigorous DNA synthetic responses to antigen E occurred with lymphocytes from all 45 subjects, including 19 highly ragweed-sensitive atop adults (8 immunotherapy treated, 11 untreated); 13 nonatopic controls; 4 newborns, and 9 agammaglobulinemic patients. The geometric mean of peak response counts per minute in all 45 subjects was 21,163 and in unstimulated cultures was 2,416 (p = less than 0.0001). The mean day on which the maximal responses occurred was 8.7, and the mean dose eliciting the maximum responses was 59 mug/ml. Statistical comparisons of the stimulated culture data revealed no significant intergroup differences. The finding of vigorous responsiveness to these purified pollen allergens by lymphocytes from nonatopic normal, newborn, and agammaglobulinemic subjects suggests that ragweed pollen antigens are either ubiquitous and lead to cell-mediated responsiveness in all subjects with intact cell-mediated inmunity, or that they may have miogenic properties in addition to their known antigenic properties.