Human lymphocyte subpopulation: early and late rosettes.

In the process of forming SRBC rosettes of human lymphocytes, two types were distinguished, the early and late rosettes. The former appeared immediately whereas the latter required further incubation at 4degreesC. In this study, the two types of cells were separated by gradient centrifugation and studied separately. It was found that the proportion of caps in the late rosettes was much greater than in the early ones. Treatment of the former by trypsin, AET, and neuraminidase decreased this proportion so that it resembled the late one. It was postulated that some of the differences in the early and late RFC lie in the differences in the content of membrane sulphydryl and sialic acid groups and distribution of SRBC receptors.