Defective mononuclear cell antibody-dependent cellular cytotoxicity (ADCC) in patients with leukocyte adhesion deficiency emphasizing on different CD11/CD18 requirement of Fc gamma RI versus Fc gamma RII in ADCC.

The defective antibody-dependent cellular cytotoxicity (ADCC) of mononuclear cells (MNC) from patients with leukocyte adhesion deficiency (LAD), beta 2 integrins (CD11a-c/CD18) deficiency was shown. LAD patients completely failed to generate MNC-ADCC against sheep red blood cells (SRBC) sensitized with murine (m) IgG2b, but had diminished but significant cytolysis against mIgG2a-SRBC, suggesting that the CD11/CD18 requirement of Fc gamma RI is different from that of Fc gamma RII in MNC-ADCC. Blocking experiments with monoclonal antibodies (mAb) against individual subunits of CD11/CD18 revealed that anti-CD18 mAb almost completely inhibited mIgG2b-mediated ADCC by normal monocytes, but only partially inhibited mIgG2a-mediated ADCC. These data may confirm the evidence that Fc gamma RII-mediated ADCC absolutely requires CD11/CD18 but Fc gamma RI-mediated ADCC does not. Among subunits of CD11/CD18, appeared to be most involved in lysis of sensitized SRBC.