Characterization of anti-asialo-GM1 monoclonal antibody

Asialo-GM1 (ASGM1) has been identified as a cell surface marker of murine NK cells. Although polyclonal anti-asialo-GM1 antibodies (anti-ASGM1 pAb) have been widely used for studying natural killer (NK) cell functions in vivo, the technical challenges have existed in their specificity for NK cell depletion. Furthermore, the exact expression of ASGM1 on the NK cell lineage and other immune cells has not been characterized due to the lack of appropriate reagents. In this context, we have recently established several clones of monoclonal antibodies against ASGM1 with different specificity to other structurally related gangliosides. In this study, we characterized the rabbit anti-ASGM1 mAb clone GA134 with both higher specificity to ASGM1 and efficacy in depleting NK cells, and the in vivo GA134 treatment significantly impaired NK cell-dependent anti-tumor effector function. We further determined the expression of ASGM1 on the NK cell lineage at distinct differentiation stages using fluorescent-labeled GA134 and found that both CD122⁺ NK1.1^- NKP and immature NK1.1⁺ CD11b^lo CD27^lo NK subsets were the earliest NK cell lineages acquiring ASGM1 expression on their cell surface. In addition to NK cells, we characterized the expression of ASGM1 on a subpopulation of T cells, mostly NK1.1⁺ T cells, and basophils.