Guanine nucleotide exchange factor (GEF) which specifically activates small GTPase CDC42 by exchanging bound GDP for free GTP (PubMed:28028151, PubMed:22461490). During immune responses, required for interstitial dendritic cell (DC) migration by locally activating CDC42 at the leading edge membrane of DC (By similarity). Required for CD4(+) T-cell migration in response to chemokine stimulation by promoting CDC42 activation at T cell leading edge membrane (PubMed:28028151). Is involved in NK cell cytotoxicity by controlling polarization of microtubule-organizing center (MTOC), and possibly regulating CCDC88B-mediated lytic granule transport to MTOC during cell killing (PubMed:25762780). Interacts (via DOCKER domain) with GTPase CDC42; the interaction activates CDC42 by exchanging GDP for GTP (PubMed:22461490, PubMed:28028151). The unphosphorylated form interacts (via DOCKER domain) with LRCH1 (via LRR repeats); the interaction prevents the association between DOCK8 and CDC42 (PubMed:28028151). Interacts with CCDC88B (PubMed:25762780). Enriched and co-localizes with GTPase CDC42 at the immunological synapse formed during T cell/antigen presenting cell cognate interaction. Translocates from the cytoplasm to the plasma membrane in response to chemokine CXCL12/SDF-1-alpha stimulation. Expressed in peripheral blood mononuclear cells (PBMCs). The DOCKER domain is necessary and sufficient for the GEF activity. In response to chemokine CXCL12/SDF-1-alpha stimulation, phosphorylated by PRKCA/PKC-alpha which promotes DOCK8 dissociation from LRCH1. The disease is caused by variants affecting the gene represented in this entry. The gene represented in this entry is involved in disease pathogenesis. A chromosomal aberration disrupting DOCK8 has been found in a patient with intellectual disability and ectodermal dysplasia. A balanced translocation, t(X;9) (q13.1;p24). A genomic deletion of approximately 230 kb in subtelomeric 9p has been detected in a patient with intellectual disability. Belongs to the DOCK family.