Flow cytometric analysis of proliferative responses of carp Cyprinus carpio peripheral blood leukocytes to mitogens and to the hemoflagellate Trypanoplasma borreli

The activation of carp peripheral blood leukocytes (PBL) was analysed radio metrically and by means of flow cytometry (FCM) in order to compare the res ults obtained with both methods. The qualitative and quantitative FCM analy ses of cellular morphology and viability resulted in a further characterisa tion of proliferative responses of carp PBL to Trypanoplasma borreli in viv o and in vitro. The lymphocyte population of PBL from T. borreli-infected c arp exhibited a marked shift in forward scattered light (FSC; cell size). W hen PBL from healthy carp were stimulated with mitogens in vitro, a lymphoi d population with increased FSC profiles was also observed. The number of t hese cells coincided to ratios of H-3-thymidine incorporation, recorded fro m corresponding cultures. Thus, it was concluded that the increase in size of stimulated lymphocytes could be due to blastogenic transformation. The a dvantage of the FCM procedure is that activation and proliferation of carp lymphocytes can be monitored without labelling the cells. Cocultures of mit ogen-stimulated carp PBL and T. borreli revealed the ability of the parasit e to suppress lymphocyte proliferation in vitro.