iC3b

iC3b is a protein fragment that is part of the complement system, a component of the vertebrate immune system. iC3b is produced when complement factor I cleaves C3b.^[1] Complement receptors on white blood cells are able to bind iC3b, so iC3b functions as an opsonin. Unlike intact C3b, iC3b cannot associate with factor B, thus preventing amplification of the complement cascade through the alternative pathway. Complement factor I can further cleave iC3b into a protein fragment known as C3d.

References

^ Robbins Basic Pathology 8th ed 2007. R Cotran, S Robbins, V Kumar, J Perkins. W.B. Saunders Company.

Pathways

Activators/enzymes

Early	C: C1 C1q C1r C1s C4 C4a C4b C2 L: MASP1/MASP2 MBL A: Factor B Factor D Factor P/Properdin
Middle	C3 C3a C3b/iC3b C5 C5a C5b C3-convertase C5-convertase
Late	MAC C5b C6 C7 C8 C9

Inhibitors

Function

Lymphoid

Antigens	Antigen Superantigen Allergen Antigenic variation Hapten Epitope Linear Conformational Mimotope Antigen presentation/professional APCs: Dendritic cell Macrophage B cell Immunogen
Antibodies	Antibody Monoclonal antibodies Polyclonal antibodies Autoantibody Microantibody Polyclonal B cell response Allotype Isotype Idiotype Immune complex Paratope
Immunity vs. tolerance	Action: Immunity Autoimmunity Alloimmunity Allergy Hypersensitivity Inflammation Cross-reactivity Co-stimulation Inaction: Tolerance Central Peripheral Clonal anergy Clonal deletion Tolerance in pregnancy Immunodeficiency Immune privilege
Immunogenetics	Affinity maturation Somatic hypermutation Clonal selection V(D)J recombination Junctional diversity Immunoglobulin class switching MHC/HLA

Substances

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This page was last edited on 1 July 2019, at 16:02