Human lymphocytes subpopulations: rabbit red blood cell rosettes.

When human lymphocytes were incubated with rabbit red blood cells (RRBC) in vitro at 4 degrees C overnight, they adhered to form rosettes. 44 +/- 4.5% of thymocytes and o.7 +/- o.3% of peripheral blood lymphocytes (PBL) formed these rosettes. The rosette-forming cells (RFC) increased to 10--40% when the PBL were stimulated by mitogens. The increases were detected 4 h after culture and reached a maximum at 24 h, thus preceding significant increases in DNA syntheses. In another set of experiments, PBL were stimulated by a range of concentrations of each of 5 mitogens. The concentrations whick led to high DNA synthesis rates also generated high percentages of the rosettes. Lastly, PBL were activated by mitogens and the effect of inhibitors of DNA synthesis, protein synthesis and ATPase activity investigated. Only the latter could inhibit the generation of the RFC. In conclusion, 1y RRBC rosettes in mitogen stimulated human PBL were markers of activated lymphocytes, 2) the percentages of RFC could constitute a reliable index of mitogenic responses, and 3) this index was independent of the usual criteria of protein and DNA synthesis.