and most importantly = and most importantly bind to the CD19 receptor?

Context:
Lymphocytes are a type of white blood cell involved in immune function and are categorized as either B-cells or T-cells. This newly discovered element, CD19-L, is expressed on the surface of T-lymphocytes and allows them to selectively bind to the CD19 receptor on the surface of B-lineage leukemia cells, and most importantly on leukemic stem cells responsible for the survival and expansion of the leukemia cell population. Once the CD19-L binds to leukemia cells, cell death occurs. Although CD19 is abundantly expressed on leukemia cells from B-lineage ALL patients, it is absent on red cells, T-cells, and normal bone marrow stem cells, making it specific, and therefore, a good therapeutic target.

More:

http://www.sciencedaily.com/releases/2011/02/110218152821.htm