Human lymphocyte subpopulations: giant human red blood cell rosettes.

Human thymus-derived (T) lymphocytes form rosettes with sheep red blood cells (SRBC) and human red blood cells (HRBC) in vitro. Twenty-four hours after inactivation by the mitogenic enzymes sodium periodate (NaIO4) and neuraminidase plus galactose oxidase (NGAO), rosette-forming cells appeared which could bind greater than or equal to 36 SRBC and greater than or equal to 21 HRBC. These were defined as giant SRBC and giant HRBC rosettes respectively. They were absent in control samples. When lymphocyte responses were assayed by the rates of DNA synthesis, they were almost eliminated by the absence of monocytes. However, the generation of giant SRBC rosettes was unaffected. The generation of giant HRBC rosettes was very significantly depressed. It was concluded that lymphocytes could still be significantly activated in the absence of monocytes. The activated lymphocytes could be recognized by their ability to form giant SRBC rosettes. In the presence of monocytes, the activated lymphocytes have the additional characteristics of being able to form giant HRBC rosettes.