CD4 molecules on CD4⁺ and CD4^locells.

The number of CD4 molecules is significantly higher on the surface of CD4⁺ than on the surface of CD4^lo T cells. Peripheral blood lymphocytes from 17 healthy people were stained with FITC–anti-CD3 and PE–anti-CD4, and the absolute numbers of CD4 molecules per cell were determined with the use of Quantibrite beads as described in “Materials and methods.” The results are shown as mean numbers of CD4 molecules per CD3⁺CD4⁺(CD4⁺), CD3⁺CD4^lo(CD4^lo), or CD3⁺CD4⁻(CD4⁻) cell (bars); vertical lines show SDs. Asterisks indicate highly significant differences between the numbers of CD4 molecules on CD4⁺ and CD4^lo cells (P < .0000001) and between CD4^lo and CD4⁻ cells (P < .000000001).