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The natural killer cell receptor Ly-49A recognizes a peptide-induced conformational determinant on its major

M Orihuela1, D H Margulies, W M Yokoyama

  • 1Department of Medicine and Pathology, Washington University School of Medicine, St. Louis, MO 63110, USA.

Proceedings of the National Academy of Sciences of the United States of America
|October 15, 1996
PubMed

Insights

Natural killer (NK) cells recognize major histocompatibility complex (MHC) class I molecules. This study shows NK cells detect peptide-induced MHC conformational changes, not specific peptides, distinguishing them from T cells.

Area of Science:

  • Immunology
  • Cellular Biology
  • Molecular Biology

Background:

  • Natural killer (NK) cells are crucial for innate immunity, inhibiting target cell lysis via interactions with major histocompatibility complex (MHC) class I molecules.
  • The Ly-49A NK cell receptor binds H-2Dd MHC class I, inhibiting NK cell activity, and was previously thought to recognize MHC class I alpha 1/alpha 2 domains without specific peptide involvement.

Purpose of the Study:

  • To investigate the role of specific peptides in NK cell recognition of MHC class I molecules.
  • To elucidate the mechanism by which NK cells distinguish between self and non-self MHC class I expression.

Main Methods:

  • Utilized alanine-substituted peptides to stabilize H-2Dd expression in transporter associated with processing (TAP)-deficient cells.
  • Employed monoclonal antibodies (mAbs) to block peptide-induced resistance and assessed stabilization of empty H-2Dd heavy chains with beta 2-microglobulin.

Main Results:

  • Stabilization of H-2Dd expression by minimal anchor motif peptides conferred resistance to NK cell lysis.
  • Peptide-induced resistance was blocked by an mAb targeting a conformational determinant on H-2Dd, not by stabilizing empty MHC class I molecules.
  • NK cell specificity for a peptide-induced conformational determinant, independent of specific peptide, was demonstrated.

Conclusions:

  • NK cells recognize a peptide-induced conformational determinant on MHC class I, distinct from the specific peptide itself.
  • This mechanism differs fundamentally from T cell recognition, suggesting NK cells respond to global MHC class I conformation or expression changes.
  • Findings support the 'missing self' hypothesis, where NK cells monitor for normal MHC class I expression.

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