Analysis by in Situ Hybridization of Cytokine Mrnas Expression in Thymic Nurse Cells

Abstract

Several observations showed that thymocytes and thymic epithelial cell lines can produce cytokines (Ceredig et al., 1986; Denning et al., 1988; Eshel et al., 1990; Ransom et al., 1987; Van der Pouw Kraan et al. 1992) and respond to their actions (Defresne et al., 1990; Everson et al., 1990; Hodgkin et al., 1990; Palacios et al., 1987; Plum et al., 1990; Ranges et al., 1988; Suda et al., 1990 a,b; Takashi et al., 1991; Watson et al., 1989). However, most of these data were obtained in vitro, often after stimulation with non physiological agents such as PMA or calcium ionophores. The first demonstration of the presence of cytokines in the thymus in situ was the detection of IL-2 and IL-4 transcripts in suspensions of non stimulated thymocytes isolated from foetuses of CBA mice (Carding et al., 1989). Later on, we demonstrated on frozen sections that mRNAs for IL-1, IL-2, IL-4, IL-6, TNFά and γIFN were present in the thymus during ontogeny following a chronological sequence (Deman. et al., 1992, 1993).