Interactions between soluble IgG, complement and cells in lymphocyte and monocyte ADCC.

Area of Science:

• Immunology
• Cellular Biology
• Biochemistry

Background:

• Antibody-dependent cell-mediated cytotoxicity (ADCC) is a crucial immune mechanism involving cytotoxic cells recognizing antibody-coated targets.
• Two primary effector cells in ADCC are K lymphocytes and monocytes, differing in their Fc receptor characteristics and interactions with IgG.
• Understanding these interactions is vital for comprehending immune responses and developing targeted therapies.

Purpose of the Study:

• To compare the functional interactions of K lymphocyte- and monocyte-mediated ADCC with monomeric and aggregated IgG.
• To investigate the influence of IgG form and complement on ADCC activity.
• To elucidate the role of Fc receptor affinity in differential ADCC responses.

Main Methods:

• Comparative analysis of K lymphocyte and monocyte ADCC assays.
• Incubation with monomeric and aggregated human IgG.
• Assessment of inhibition by IgG, complement-bound aggregates, and adherent cells.

Main Results:

• K lymphocyte ADCC was inhibited by aggregated IgG but not monomeric IgG.
• Monocyte ADCC was inhibited by both monomeric and aggregated IgG, suggesting high-affinity Fc receptors.
• Complement binding reduced aggregate-induced inhibition of K lymphocyte ADCC; adherent cells inhibited K lymphocyte ADCC only without IgG.

Conclusions:

• K lymphocyte ADCC exhibits properties consistent with a significant in vivo role due to differential sensitivity to IgG forms.
• Monocyte ADCC is strongly inhibited by physiological IgG concentrations, potentially limiting its in vivo efficacy.
• Differences in Fc receptor affinity likely underlie the distinct ADCC profiles of K lymphocytes and monocytes.