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The aim of this study was to characterize the cytokine secretion patterns of human T helper cells from healthy donors reactive with somatic antigens from various bacteria, the nematode Anisakis and tetanus toxoid. From the peripheral blood of four healthy donors we have established 70 T cell lines reactive with antigens from Yersinia, Salmonella, Morganella, Klebsiella, Serratia, Escherichia, Chlamydia, Shigella, Streptococcus, tetanus toxoid and Anisakis, respectively. Our results show that all T cells reactive with bacteria produce interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), but no interleukin (IL)-4 and no or very little IL-2 and IL-10 and, thus, belong to the Th1 subset, while T cells reactive with tetanus toxoid or Anisakis belong to the Th0 subset with production of IFN-gamma, IL-2, IL-4, IL-10 and TNF-alpha. In summary, our data further substantiate the concept of a functional diversity of human T helper cells with respect to their cytokine profiles. Furthermore, they indicate that a Th1 cytokine profile is not restricted to intracellular bacteria.

Two methods are described for determination of the microphonic generator transfer characteristic using data from bitonal stimulation experiments. In one method, the filtered high-frequency microphonic output component is measured at the extreme points of the modulation envelope for a sequence of intensity levels of the lower-frequency component. This method is applied to data derived from a modulation test procedure making use of a wide range of test intensities for both the high- and low-frequency components and also to data generated in a test using a single sequence of stimuli with increasing intensity of the lower frequency. In a second method, the modulation envelope of the higher-frequency microphonic response to a bifrequency acoustic stimulus is used to determine a segment of the generator transfer characteristic. The results of a sequence of determinations for different lower-frequency intensities show good agreement with each other and with the transfer characteristic derived by the first method. However, the second method shows that there is an appreciable level-dependent hysteresis, the mechanism for which has not been determined. The transfer characteristics determined would give rise to a pronounced dc rectification component in the direction of positive summating potential.