Recombinant interleukin 2-activated natural killer cells regulate IgG2a production

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Abstract
In this report we have analyzed the effect of recombinant interleukin 2 (rIL 2) and rIL 2‐activated natural killer (NK) cells on the production of immunoglobulin isotypes by lipopolysaccharide (LPS)‐stimulated spleen cells from nude mice. We found that rIL 2 induced a dose‐dependent increase of IgG2a secretion and a concomitant inhibition of the secretion of other Ig isotypes. The analysis of the phenotype of LPS‐ and LPS+rIL 2‐stimulated nude spleen cells showed the appearance of a Thy‐1+asialo GM‐1+slgM−CD3−CD4−CD8− cell population in the presence of rIL 2. A population with a similar phenotype was generated upon stimulation of spleen cells from nude mice with rIL 2 alone. These cells lysed YAC‐1 cells, did not contain the α or γ transcripts encoding the corresponding T cell receptor chains and are therefore NK cells activated by rIL 2. In co‐culture experiments, these cells selectively increased the secretion of IgG2a by LPS‐stimulated splenocytes from nude mice. The IgG2a induction triggered by rIL 2‐activated NK cells, as well as that triggered by rIL 2, were blocked by an anti‐interferon γ monoclonal antibody. Thus, rIL 2 activated‐NK cells enhance the production of IgG2a by secreting interferon‐γ.