Common precursor pool marker for allospecific (CTL) and nonspecific (NK and activated) cytotoxic cells in the bone marrow.

A recently described monoclonal mouse IgG1 antibody, NK-9, reacts with practically all peripheral blood large granular lymphocytes (LGL). It also detects a population of non-LGL lymphoid cells that harbors precursor cells for both nonspecific activated killer (AK) and allospecific killer cells. In the bone marrow, the NK-9-positive population represented 9% of all nucleated cells, which was 40% of all lymphoid cells. This population was initially noncytotoxic, but when appropriately stimulated the NK-9-positive cells gave rise to AK and allospecific cytotoxic cells, whereas no such activity could be generated from the NK-9-negative cells. When the NK-9-positive cells were cultured with high concentrations of T cell growth factor, the results were cultures consisting of over 80% cells with LGL morphology and exhibiting effective cytotoxicity against K562 targets. It is concluded that the precursor cells for various modes of nonspecific and antigen-specific cytotoxicity are related and appear to be harbored in the NK-9-positive pool in the bone marrow.