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Circulating immune complexes (CICs) act as an adjuvant and uptake of ICs via Fc-receptors enhances the antigen presentation. The opsonization of ICs with complement make them pathogenic and this lead to their tissue deposition at the vascular sites, causing organ damage. Thus, to measure the pathogenic ICs, it is essential to measure the amount of complement bound to the CICs. Both C3d and C4d are suggested to be the biomarker for humoral rejection, and they facilitate the formation of immune deposits in the tissue. Now it is recognized that human CD4+ T cells upon activation express low affinity Fc receptors and signal via CD16a receptor, which contribute to the generation of TH1, TH17 and Tfh cells. Recently, it was further shown that those CD4+ T cells that express low affinity CD32a also demonstrate the enrichment of HIV-1 provirus. Company support studies to identify those CD4+ T cells that express low affinity Fc receptors, which bound to ICs. A proposed model for possible interaction of soluble immune complexes with integrin protein on cell surface is shown.

ProGen’s provides and support technology in the following areas:

  • Use of CIC based approaches in the identification of the antigenic epitopes for the development of new vaccines.
  • Purification and proteomic analysis of CIC to identify biomarkers.
  • Identification of Fc receptor enrichment on various lymphocyte populations.
  • Developing assays for prescreening of humanized antibody-based drugs.
  • Purification of CICs to develop immune complex proteome. This focus could also lead the development of new protein-based therapeutics.

The complement proteins C1q, C3, C4, and C5 are observed bound to CICs. Complement regulatory proteins Vitronectin and Clusterin that are bound to CIC are present at elevated levels in the plasma compared to soluble MAC (C5b-9).

Plasmapheresis strips the complement bound to CICs. An effect of dilution is observed on IgG-CIC, while a disproportionate loss of C4 bound to CIC is observed post therapy.

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