Alterations of NK Cell Phenotype During Pregnancy in Multiple Sclerosis.

In multiple sclerosis (MS), relapse rate is decreased by 70-80% in the third trimester of pregnancy. However, the underlying mechanisms driving this effect are poorly understood. Evidence suggests that CD56 ^bright NK cell frequencies increase during pregnancy. Here, we analyze pregnancy-related NK cell shifts in a large longitudinal cohort of pregnant women with and without MS, and provide in-depth phenotyping of NK cells. In healthy pregnancy and pregnancy in MS, peripheral blood NK cells showed significant frequency shifts, notably an increase of CD56 ^bright NK cells and a decrease of CD56 ^dim NK cells toward the third trimester, indicating a general rather than an MS-specific phenomenon of pregnancy. Additional follow-ups in women with MS showed a reversal of NK cell changes postpartum. Moreover, high-dimensional profiling revealed a specific CD56 ^bright subset with receptor expression related to cytotoxicity and cell activity (e.g., CD16 ⁺ NKp46 ^high NKG2D ^high NKG2A ^high phenotype) that may drive the expansion of CD56 ^bright NK cells during pregnancy in MS. Our data confirm that pregnancy promotes pronounced shifts of NK cells toward the regulatory CD56 ^bright population. Although exploratory results on in-depth CD56 ^bright phenotype need to be confirmed in larger studies, our findings suggest an increased regulatory NK activity, thereby potentially contributing to disease amelioration of MS during pregnancy.
Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2022 Wisgalla, Ramien, Streitz, Schlickeiser, Lupu, Diemert, Tolosa, Arck, Bellmann-Strobl, Siebert, Heesen, Paul, Friese, Infante-Duarte and Gold.)