Two natural killer cell populations which belong to T cell lineage in nude mice.

Enriched natural killer (NK) cell populations from BALB/c nude mice obtained by using nylon wool column (NWC) separation were stained with anti-Thy-1 and anti-asialo GM1 (GA1), and then were fractioned by flow cytometry into 4 cell populations: Thy-1+GA1+ cells, Thy-1+GA1- cells, Thy-1-GA1+ cells and Thy-1-GA1- cells. These cell populations were sorted out by flow cytometry and were examined for NK activity. Of the sorted cells, high NK activity was found in the two populations, Thy-1+GA1+ cells and Thy-1-GA1+ cells. In the other populations expressing Thy-1 antigen alone or expressing neither GM1 nor Thy-1, NK activity was almost undetectable. The two cell populations with NK activity were lineaged with respect to rearrangement of the T cell receptor genes. Southern gel analysis using a cDNA probe containing the D beta 1, J beta 1.3 and C beta 1 genes of the T cell receptor showed a reduction of the germ-line band of DNA in the 3 fractionated populations other than Thy-1-GA1- cells. Since these observations were demonstrated in nude spleen cells, it is indicated that the cells with NK activity belong to T cell lineage even if they lack Thy-1 expression and that they may develop out of the thymus, if they express Thy-1 antigen.