THE ROLE OF NK CELLS DURING IN-VIVO ANTIGEN-SPECIFIC ANTIBODY-RESPONSES

Investigations into the role of NK cells in regulating Ab responses ha ve yielded variable results, some suggesting that NK cells can down-re gulate Ag-specific Ig production and others proposing an enhancing eff ect. These apparently inconsistent findings may stem partially from th e specificity of reagents used in purifying cell populations and/or th e nature of the in vitro systems used to study these events. We chose to investigate the ability of either resting or poly(I:C)-activated NK cells to alter an in vivo Ab response in mice given a T-independent ( TNP-LPS) or T-dependent (TNP-keyhole limpet hemocyanin (KLH)) Ag. By u sing a more specific Ab, anti-NK-1.1, to deplete NK cells, we were abl e to clearly show that resting, endogenous NK cells do not affect eith er type of response, as measured by serum Ag-specific Ig levels quanti tated by isotype-specific ELISA. In contrast, activation of NK cells b y poly(I:C) increased Ag-specific IgC2a as well as IgG1 levels. Intere stingly, only the effect on IgG2a production is reversible by depletio n of NK cells.