Predict the ADCC Extent: CD2posCD16Apos NK Phenotype

Background

Predicting the extent of Antibody-Dependent Cellular Cytotoxicity (ADCC) involves understanding the phenotypic characteristics of natural killer (NK) cells involved in the process. The CD2posCD16Apos NK phenotype refers to a subset of NK cells expressing both the CD2 and CD16A cell surface markers. Here's how this phenotype might relate to ADCC:

• CD2 Expression: CD2 is a cell adhesion molecule found on the surface of NK cells. NK cells expressing CD2 may have enhanced cytotoxicity and cytokine production upon activation.
• CD16A Expression: CD16A, also known as FcγRIIIA, is a low-affinity Fc receptor expressed on NK cells. It binds to the Fc portion of antibodies (such as those involved in ADCC) and mediates the destruction of antibody-bound target cells.

NK cells expressing both CD2 and CD16A may be particularly efficient in mediating ADCC for several reasons:

• Enhanced Activation: CD2 expression on NK cells may lead to enhanced activation upon encountering target cells, priming them for cytotoxic activity.
• Efficient Antibody Binding: CD16A allows NK cells to bind to the Fc portion of antibodies, including those involved in ADCC. This receptor-ligand interaction triggers NK cell activation and cytotoxicity against antibody-coated target cells.
• Synergistic Effects: The co-expression of CD2 and CD16A may lead to synergistic effects, enhancing NK cell activation and cytotoxicity when encountering antibody-bound target cells.

Research Results

Lethal frequency indicates serial ADCC and donor-to-donor variability.
Fig.1 Lethal frequency indicates serial ADCC and donor-to-donor variability.1,2	The killing frequency (KF) of each E:T in the ADCC assay can be directly determined by dividing the percentage of target cells killed by the percentage of dead cells. Specifically, at an E:T of 1:4, 25% of the targets will be killed, i.e. a KF of 1.0. When the kill rate of this E:T is 48%, the KF is 1.9 (as shown in Fig.1 A).
Effect of CD16A genotype on ADCC KFs.
Fig.2 Effect of CD16A genotype on ADCC KFs.1,2	Similar tandem ADCCs were shown by comparing F/F to V/F and V/V genotypes (Fig.2 A). The CD16A genotype has previously reported effects, indicating that our samples have typical characteristics (Fig.2 B-C).
NK phenotypic markers are assessed to predict KF.
Fig.3 NK phenotypic markers are assessed to predict KF.1,2	CD16A expression was similar in the high and low KF groups (Fig.3 A-B). However, no differences were detected in perforin levels (Fig.3 C). In addition, the percentage of CD2pos for donor CD16Apos NKs with high KFs was much higher than that for low KFs (Fig.3 D). The amount of CD2 expressed by CD2pos cells was similar in both groups (Fig.3 E). The above data suggest that CD2posCD16Apos NK cells have enough CD2 to enhance signaling, independent of KF status.
KFs are predicted by %CD2pos in CD16Apos NK cells.
Fig.4 KFs are predicted by %CD2pos in CD16Apos NK cells.1,2	The results showed that the percentage of CD2pos in CD16Apos NK cells was positively correlated with KF (Fig.4 A). In addition, the %CD2pos of CD16Apos NK cells was shown to have a good predictive value for KF by ROC analysis (Fig.4 B).

Conclusion

This study shows that there is a wide variation in serial ADCC between human donors. These differences can be predicted by the %CD2pos of CD16Apos NK cells.

References

1. Tang, Jennifer J-J et al. "Natural killer (NK) cell expression of CD2 as a predictor of serial antibody-dependent cell-mediated cytotoxicity (ADCC)." Antibodies. (2020) 9,4 54.
2. Distributed under Open Access license CC BY 4.0, without modification.