Viral infection modulates Qa-1b in infected and bystander cells to properly direct NK cell killing

Area of Science:

• Immunology
• Virology
• Cellular Biology

Background:

• Natural killer (NK) cell activation is governed by a balance of activating and inhibitory receptors, including CD94-NKG2 complexes.
• The Qa-1b ligand and CD94-NKG2 receptors on NK cells are crucial for resistance to ectromelia virus (ECTV) infection in C57BL/6 mice.

Purpose of the Study:

• To investigate the role of NKG2C/NKG2E deficiency and Qa-1b expression levels in ECTV infection.
• To elucidate the mechanism by which NK cells interact with infected and bystander cells during viral infection.

Main Methods:

• Analysis of ECTV-infected mice with deficiencies in NKG2C or NKG2E.
• Assessment of Qa-1b expression in infected cells, inflammatory monocytes, and B cells.
• In vitro and in vivo killing assays using NK cells and cells with varying Qa-1b expression.

Main Results:

• NKG2C or NKG2E deficiency did not alter susceptibility to lethal ECTV infection.
• Overexpression of Qa-1b in infected cells increased susceptibility to ECTV.
• Qa-1b was down-regulated in infected cells and up-regulated in bystander inflammatory monocytes and B cells.
• Activated NK cells killed Qa-1b-deficient cells effectively in vitro and in vivo.

Conclusions:

• Recognition of Qa-1b by activating CD94/NKG2 receptors is not the primary factor during viral infection.
• Modulation of Qa-1b expression levels on infected and bystander cells is critical for regulating NK cell-mediated killing during ECTV infection.