NKG2A inhibits TH2 cell effector function in vitro

Abstract

Background: We previously reported that NKG2A, a key inhibitory ligand for HLA-E, is expressed on activated TH2 but not TH1 cells. Here we measured cytokine expression in human ex vivo TH2 cells upon activation with anti-CD3/28 and challenge with an NKG2A-specific agonist.

Methods: TH2 cells were purified from healthy volunteers and activated with anti-CD3/28 in the presence and absence of NKG2A-specific agonist. IL-4 was used as a marker of TH2 effector function and measured by flow cytometry.

Results: Activation of TH2 cells increased NKG2A positivity from (Mean +/- SE) 7.3 +/- 2.4% to 13.7 +/- 3.8%; (p = 0.03). The presence of NKG2A agonist did not significantly alter NKG2A expression, however, the percentage of activated TH2 cells expressing intracellular IL-4 decreased from 25.5 +/- 6.8% to 9.3 +/- 4.8% (p = 0.001).

Conclusion: We show that signalling through NKG2A suppresses TH2 effector function. This may provide a means to modulate Th1/Th2 balance in diseases where Th2 cytokines predominate.

Figure 1

Comparison of intracellular IL-4 expression between culture conditions. Comparison of TH2 lymphocytes cultured in each of four culture conditions. Mean ± SEM percent cells positive for intracellular IL-4 is shown in this graph.

Figure 2

Representative flow cytometry comparison of surface NKG2A and intracellular IL-4 co-expression between culture conditions. Flow cytometry comparison of NKG2A and IL-4 co-expression for an exemplary sample of TH2 cells cultured with CD3/CD28 antibodies (positive control) and soluble CD3/CD28/NKG2A antibodies (A). The accompanying histogram shows the similar decrease in overall IL-4 expression in the same positive control (outlined) and Anti-NKG2A samples (shaded) (B). Analyses were gated by forward and side-scatter properties and on CD3+CD4+ cells.