Complement receptor type 1 (CR1, CD35) expression on peripheral T lymphocytes: both CD4- and CD8-positive cells express CR1.

T lymphocytes from 42 healthy blood donors were examined for expression of CR1 on the cell surface using a fluorescence-activated cell sorter. The fraction of CR1-positive T lymphocytes varied in the range from 1 to 8% (median 2.4%). The CR1-positive T lymphocytes constituted a homogeneous group of cells regarding both size and granulation; they seemed to be larger and more granulated than the average T lymphocytes. The CR1-expressing T lymphocytes were found both in the CD4- and in the CD8-positive subpopulations of T lymphocytes, and although the CD4-positive cells expressed CR1 with a slightly higher percentage than did the CD8-positive cells, this difference was not significant. The number of CR1-positive T lymphocytes did not correlate with the level of CR1 on erythrocytes. The presence of CR1 on a small T lymphocyte population suggests that CR1 on T lymphocytes might play a role in the immune regulation.