Different DOCK2 mutations resulted in absent or significantly reduced levels of DOCK2 protein expression that precede a chain of immunological defects including CD4 + and CD8 + T cells lymphopenia with reduced T cell receptor excision circles (TRECs), diminished phytohemagglutinin (PHA)-induced T cell proliferation, impaired NK cell function, decrease B cell counts, and defective antibody responses in DOCK2-deficient patients [3]. Here, DOCK2 is linked to lymphopenia.