Expression of Lck in normal CD5⁺ B cells. Immunoblot analysis using an anti-Lck MoAb of lysates from normal B cells from different lymphoid organs. On the right is shown a similar immunoblot of lysates of total cord blood B cells (CB), as well as of the purified CD5⁻ and CD5⁺ B-cell populations from the same cord blood sample. A lysate from normal T cells is included as a positive control. PB, resting peripheral blood B cells; PB act, peripheral blood B cells activated by surface IgM cross-linking; spleen, B cells purified from spleen; adenoid, B-cells purified from adenoid, CB, cord blood B cells.