Active and late rosette-forming cells: immunological and cytochemical characterization

In order to characterize T-cell subpopulations with different affinities for sheep red blood cells, a possible correlation between active and late rosette-forming cells (RFC), expression of Fc receptors, and the presence of Ia antigens was investigated. Further analysis of their spontaneous in vitro DNA synthesis, and their cytochemical pattern was also performed. Most of the active T cells lacked Fc receptors and expressed Ia antigens, whereas the large majority of cells with Fc-IgG and -IgM receptors were included as late T cells, but lacked Ia determinants. Analysis of spontaneous blastogenesis showed that late RFC, but not active RFC, synthesize DNA in unstimulated cultures. Cytochemical analysis suggested that Active RFC display a more immature phenotype compared to late RFC, which have enzymatic markers present in mature T cells. Possible interpretations of these findings are discussed. © 1981.