This study investigates the formation of nonimmune rosettes by human T and B lymphocytes with sheep red blood cells (SRBC). The authors found that a large population of lymphocytes (52-81%) from peripheral blood and thymus formed E rosettes, which are not dependent on immunoglobulin receptors. These rosettes were blocked by pretreatment with anti-Ig sera and were temperature-dependent, disintegrating at 37°C. The rosette-forming ability could be restored by culturing trypsinized lymphocytes, suggesting the presence of a rapidly released or metabolized receptor substance. The study also noted that EAC-binding lymphocytes, which are considered B cells, did not bind SRBC, and that chronic lymphatic leukemia patients had low E binding and high anti-Ig activity. The findings suggest that this marker could be useful for reclassifying lymphoid diseases and characterizing immunological status in various conditions.This study investigates the formation of nonimmune rosettes by human T and B lymphocytes with sheep red blood cells (SRBC). The authors found that a large population of lymphocytes (52-81%) from peripheral blood and thymus formed E rosettes, which are not dependent on immunoglobulin receptors. These rosettes were blocked by pretreatment with anti-Ig sera and were temperature-dependent, disintegrating at 37°C. The rosette-forming ability could be restored by culturing trypsinized lymphocytes, suggesting the presence of a rapidly released or metabolized receptor substance. The study also noted that EAC-binding lymphocytes, which are considered B cells, did not bind SRBC, and that chronic lymphatic leukemia patients had low E binding and high anti-Ig activity. The findings suggest that this marker could be useful for reclassifying lymphoid diseases and characterizing immunological status in various conditions.