α2β1 Integrin Is Required for Optimal NK Cell Proliferation during Viral Infection but Not for Acquisition of Effector Functions or NK Cell-Mediated Virus Control

NK cells play an important role in antiviral resistance. The integrin alpha 2, which dimerizes with integrin beta 1, distinguishes NK cells from innate lymphoid cells 1 and other leukocytes. Despite its use as an NK cell marker, little is known about the role of alpha 2 beta 1 in NK cell biology. In this study, we show that in mice alpha 2 beta 1 deficiency does not alter the balance of NK cell/innate lymphoid cell 1 generation and slightly decreases the number of NK cells in the bone marrow and spleen without affecting NK cell maturation. NK cells deficient in alpha 2 beta 1 had no impairment at entering or distributing within the draining lymph node of ectromelia virus (ECTV)-infected mice or at becoming effectors but proliferated poorly in response to ECTV and did not increase in numbers following infection with mouse CMV (MCMV). Still, alpha 2 beta 1-deficient NK cells efficiently protected from lethal mousepox and controlled MCMV titers in the spleen. Thus, alpha 2 beta 1 is required for optimal NK cell proliferation but is dispensable for protection against ECTV and MCMV, two well-established models of viral infection in which NK cells are known to be important.