Cell surface DNA in immunosuppression in AKR leukemia.

Spleen cells from leukemic AKR mice contain nonspecific T suppressor cells that suppress the in vitro anti-SRBC responses of normal AKR spleen cells. The suppression is abrogated by pretreatment of the leukemic cells with DNase. Cells with surface DNA can be enriched by treatment with anti-DNA antibodies and removed on anti-Ig columns. Even though there is a 10-fold enrichment in suppression by the surface DNA-positive cells (DNA+), the depleted population (DNA-) still suppresses with an efficiency comparable to the unfractionated spleen cells. Pretreatment with anti-I-J antiserum and separation on columns neither enriches nor depletes suppressor cells. Fractionating leukemic spleen into 4 populations of cells by sequential treatment with anti-DNA and anti-I-J with separation on appropriate columns, resulting in 4 populations (DNA+/I-J-, DNA+/I-J+, DNA-/I-J+, and DNA-/K-J-), revealed that the DNA+/I-J- cells that comprise ca. 15% of the total are the most potent suppressors. The DNA+/I-J+ cells that comprise ca. 2% of the cells are less efficient and their suppression is not sensitive to DNase. The DNA-/I-J+ population (ca. 10% of the total) are also poor suppressors. The remaining cells, which are DNA-/I-J-, do not act as suppressors. When small numbers of any 2 of the 4 fractions were added together, it was found that the DNA+/I-J- cell can interact with the DNA+/I-J+ and the DNA-/I-J+ cells but not the DNA-/I-J- cells to give enhanced suppression.