Hepatic uptake of small-latticed immune complexes does not alter mononuclear phagocyte system function

Area of Science:

• Immunology
• Hepatology
• Cell Biology

Background:

• Immune complexes (ICs) play a role in various immune responses.
• The mononuclear phagocyte system (MPS) is crucial for clearing circulating particles.
• The size and lattice structure of ICs may influence their clearance and biological effects.

Purpose of the Study:

• To investigate the hepatic and splenic uptake of small-latticed immune complexes.
• To determine the effect of small-latticed ICs on the function of the hepatic mononuclear phagocyte system (MPS).

Main Methods:

• Preparation of small-latticed immune complexes at fifty-fold antigen excess.
• Quantification of the clearance and organ uptake of aggregated human IgG and aggregated mouse albumin as MPS probes.
• Administration of varying doses of small-latticed ICs to mice to assess MPS function.

Main Results:

• Hepatic uptake of small-latticed ICs was comparable to large-latticed ICs at 1 hour but significantly less at later time points.
• Splenic uptake of small-latticed ICs was lower than large-latticed ICs at all time points.
• Doses of small-latticed ICs (1-5 mg antibody) did not inhibit MPS probe clearance or uptake, unlike large-latticed ICs which caused dose-dependent delays.

Conclusions:

• Small-latticed immune complexes are inefficiently cleared by the hepatic MPS.
• The presence of substantial amounts of circulating small-latticed ICs does not impair MPS function.