Participation of cytoplasmic organelles in E-rosette formation.

To elucidate the mechanism of E-rosette formation between T cells and sheep red blood cells (SRBC), the effect of various agents affecting the function of cytoplasmic structures (microtubules and microfilaments) and organelles (mitochondria and rough endoplasmic reticulum) was investigated. E-rosette formation was greatly inhibited by agents that block either the energy producing system (KCN and NaN3) or the integration of microfilaments (cytochalasin B, dihydrocytochalasin B and cytochalasin D). On the other hand, there was little or no suppression by either inhibitors of protein synthesis (cycloheximide and puromycin), agents that block the polymerization of microtubules (colchicine, podophyllotoxin and vinblastine), or chemicals disconnecting surface membrane proteins from the intracellular structural proteins (chlorpromazine, dibucaine, hydrocortisone, and propranolol). The calcium ionophore A23187, which transports Ca2+ into the cytosol, inhibited the E-rosette formation in the presence of Ca2+, but not in its absence. From these results, we concluded that new synthesis of ATP and the structural integration of microfilaments are indispensable for the E-rosette formation, which is triggered by an interaction between the ligand (T11TS) and its corresponding receptor (CD2). A certain level of intracellular Ca2+ is also involved in the E-rosette formation.