Natural Killer (NK) Cell Expression of CD2 as a Predictor of Serial Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC).

Jennifer J.-J Tang,Lydia Navarrete-Galvan,Dorothy Hudig,Doug Redelman,Michael J Guglielmo,Julie Smith-Gagen,Alexander P Sung

doi:10.3390/antib9040054

Abstract

NK cell ADCC supports monoclonal antibody anti-tumor therapies. We investigated serial ADCC and whether it could be predicted by NK phenotypes, including expression of CD16A, CD2 and perforin. CD16A, the NK receptor for antibodies, has AA158 valine or phenylalanine variants with different affinities for IgG. CD2, a costimulatory protein, associates with CD16A and can augment CD16A-signaling. Pore-forming perforin is essential for rapid NK-mediated killing. NK cells were monitored for their ADCC serial killing frequency (KF). KF is the average number of target cells killed per cell by a cytotoxic cell population. KF comparisons were made at 1:4 CD16pos NK effector:target ratios. ADCC was toward Daudi cells labeled with 51Cr and obinutuzumab anti-CD20 antibody. CD16A genotypes were determined by DNA sequencing. CD2, CD16A, and perforin expression was monitored by flow cytometry. Serial killing KFs varied two-fold among 24 donors and were independent of CD16A genotypes and perforin levels. However, high percentages of CD2pos of the CD16Apos NK cells and high levels of CD16A were associated with high KFs. ROC analysis indicated that the %CD2pos of CD16Apos NK cells can predict KFs. In conclusion, the extent of serial ADCC varies significantly among donors and appears predictable by the CD2posCD16Apos NK phenotype.

Highlights

Antibody-dependent cell-mediated cytotoxicity (ADCC) is critical for many monoclonal antibody therapies directed toward tumors
ADCC by B cells within the peripheral blood mononuclear cells (PBMCs) that would occur if anti-CD20 antibody were present in the assays); and (3) use of unfractionated PBMCs with TruCount® beads to determine the numbers of CD16A receptor-positive effector (E) natural killer (NK) cells within the PBMCs
We report variability in serial ADCC by an unstimulated NK cell population that represents the state of NK cells in vivo

Summary

Introduction

Antibody-dependent cell-mediated cytotoxicity (ADCC) is critical for many monoclonal antibody (mAb) therapies directed toward tumors. ADCC involves a virally infected or tumor “target” cell with antigens, IgG1 or IgG3 antibodies that bind to the antigens, and effector cytotoxic cells with receptors for the antibody, reviewed [1]. Both natural killer (NK) lymphocytes and macrophages can be ADCC effector cells. Tumors can escape from attack by outgrowth of variants lacking the critical antigen [7] but there has been little attention given as to how the extent of variations in ADCC capacity could contribute to patient outcomes

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