RAC2 and Immunodeficiency: While demonstrating a crucial involvement of SDF-1/CXCR4-mediated Rac2 activity in limiting neutrophil mobilization, zebrafish models of primary immune deficiency caused by human RAC2 mutations or morpholino approaches indicate that the pathogenic role for RAC2 in immune cell physiology (Hsu et al., 2019; Sharapova et al., 2019; Lagresle-Peyrou et al., 2020) is linked to an altered PI3K-mediated cell polarity signaling in neutrophil migration during an inflammatory response (Deng et al., 2011).