Antigen-reaktive CD4+ T-Zellen spielen eine wichtige Rolle bei der Entwicklung schützender Immunität. So sind Kenntnisse über die Bildung und Erhaltung CD4+ T-Zellen möglicherweise bedeutend für die Entwicklung verbesserter Impfstoffe und neuer Therapieansätze bei akuten und chronischen Infektionserkrankungen. Mit dieser Arbeit wurde eine genaue Charakterisierung CD4+ T-Zell-Antworten im Vergleich zu CD8+ T-Zellen am Infektionsmodell der murinen Listeriose vorgenommen. So konnten erstmals wichtige Unterschiede zwischen den beiden T-Zell-Kompartimenten beschrieben werden, insbesondere die Beobachtung, dass - im Gegensatz zu CD8+ T-Zellen - CD4+ Effektor-Gedächtniszellen nach bakterieller Infektion kontinuierlich im gesamten Organismus über die Zeit abnehmen.

In cultured medaka testis fragments, cells remained viable for the entire culture period (17h), and spermatids that developed from spermatocytes were viable and motile. Primary cultures were characterized over a period of two days with respect to cell viability and the distribution of adherent and suspended cells. These two cell populations were maintained in dynamic equilibrium in vitro for several days. Proliferating cells were predominant among clusters of suspended cells, as determined by BrdU labeling, and CFSE and propidium iodide PI labeling. Based on cytological criteria, the proliferating cells were mostly spermatogonia and possibly also preleptotene spermatocytes. Differentiation of spermatocytes into spermatids or spermatozoa was also observed, mainly among the suspended cells. These results suggest that the organ and primary culture systems are suitable systems for studying the effects of substances that interfere with spermatogenesis in the medaka, a model vertebrate. The organ and primary culture systems were used to analyze the effects of a synthetic estrogen, EE2, on cell proliferation in medaka testis. Both organ and primary culture were suitable for this purpose consistently small concentrations (0.01 and 1 nM) of EE2 stimulated cell proliferation slightly, while higher concentrations (100 nM) had an inhibitory effect. To investigate the effect of phytoestrogens on cell proliferation in spermatogenesis, selected flavonoids [genistein (1, 10, 100 µg/ml), quercetin (0.01, 1, 100 µM), and 8-prenylnarigenin (0.001, 0.1, 1, 10 µM)] were added to medaka testis primary cultures. Genistein and quercetin inhibited cell proliferation in the cultures while 8-prenylnarigenin had no effect. In a second series of experiments the addition of genistein (10 µg/ml) to primary cultures significantly inhibited both cell proliferation and cell differentiation as determined by flow cytometry using CFSE/PI labeling.