The importance of RIAM and Talin in integrin activation is highlighted by the effect of their deletion, where knockout mice display a phenotype reminiscent of Leukocyte Adhesion Deficiency (LAD) syndromes, with a pronounced neutrophilic (4-fold increase) and monocytic leukocytosis for RIAM-/- mice that is even more pronounced for Talin1-/- mice (>30-fold increase). Here, APBB1IP is linked to Increased total leukocyte count.