PHENOTYPIC AND FUNCTIONAL-CHARACTERIZATION OF A PANEL OF CYTOTOXIC MURINE NK CELL CLONES THAT ARE HETEROGENEOUS IN THEIR ENHANCEMENT OF IG SECRETION IN-VITRO

NK cells not only function as cytotoxic effector cells, but also have immunoregulatory roles including the enhancement of Ig secretion. To h ave a stable and uniform population of NK cells to study their role in Ig secretion, we generated murine NK clones. Thus, culture of splenoc ytes from mice that were homozygous for a mutation in the p53 tumor su ppressor gene (p53-KO) with IL-2 and poly(IC) resulted in a long-term NK line, from which four stable clones were derived. This approach als o yielded a long-term NK line from splenocytes of normal C57BL/6 mice. Identification of the clones as members of the NK lineage was based o n large granular morphology, expression of NK-TR and absence of TCR ge ne rearrangement. Flow cytometry revealed that all clones expressed IL -2R alpha and beta, chains and B220, but no CD3, NK1.1, DX5 or Ly-49, RT-PCR analysis showed heterogeneity in NK1.1 gene expression, and dem onstrated expression of perforin and several granzymes in all clones. Three out of four clones lysed YAC-1, but not P815 target cells, corre sponding to a pattern of NK specificity. All NK clones enhanced Ig sec retion in an in vitro model for T cell-independent type 2 antigens, al beit to varying degrees. We found no correlation between the degree of helper activity of the NK clones and the revel of their cytotoxic act ivity on YAC-1 targets. Thus, we established murine NK clones, and sho w that they mediate both cytotoxicity and enhancement of Ig secretion.