The effect of addition of antigens to cultures of lymphocytes from atopic individuals was investigated. The number of large "blast cells" in cultures of patients sensitive to ragweed, Alternaria, and penicillin was greater than in control cultures from non-sensitive individuals, supporting the specific stimulatory effect of antigen. For each antigen, there is an optimal dose-response curve. Above this optimal concentration no further stimulatory effect is obtained. When two or more antigens to which a patient is sensitive were added to his lymphocytes, no cumulative stimulatory effect was obtained, as compared with the effect of only one antigen. A similar absence of summation could be seen when an antigen was mixed with phytohemagglutinin. Although the morphology of the blast cells obtained with antigenic stimulation was similar or identical to that obtained with phytohemagglutinin (PHA), the percentage of blast cells was strikingly higher with PHA, and the peak of response appeared after 3 days with PHA instead of 5 to 7 days as with antigens. When the percentage of blast cells obtained with ragweed and Alternaria was compared with other tests of hypersensitivity, such as, skin test and passive hemagglutination, a fairly good correlation was observed. On the other hand, penicillin-sensitive patients can exhibit a positive hemagglutination test and an increased percentage of blast cells with a negative skin test. When antigen was added to the washed lymphocytes of a patient sensitive to that particular antigen, the culture fluid contained antibodies demonstrable by the Schultz-Dale technique. The highest content was observed from the third to the fifth day with a significant decrease at the seventh and ninth days. Heating this culture fluid at 56° C. for 4 hours significantly decreased the content in antibodies. The addition of fluid from lymphocytes grown in tissue culture in the presence of antigen caused contraction of unsensitized monkey ileum strip. This conceivably could be due to the presence of antigen-antibody complexes.
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