iC3b

iC3b is a protein molecule that is used in medical research because of its ability to bind to specific target cells. This is useful for basic research, and in some cases it is possible to get the immune system to attack those cells, thus opening the possibility of new cancer treatments.

iC3b is a proteolytically inactive product of the complement cleavage fragment C3b^[1] that still opsonizes microbes, but cannot associate with factor B, thus preventing amplification of the complement cascade or activation through the alternative pathway.

References

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

Proteins: complement system (C, L, A)

Activators/enzymes

Early	C: 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 C3-convertase C5-convertase

Late	MAC C6 C7 C8 C9

Inhibitors

CL: C4BP

A: Factor H

Complement receptors

Immunology: lymphocytic adaptive immune system and complement

Lymphoid

Antigens	Antigen Superantigen Allergen 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 inaction: Tolerance Central Peripheral Clonal anergy Clonal deletion Tolerance in pregnancy Immunodeficiency

Immunogenetics	Affinity maturation (Somatic hypermutation Clonal selection) V(D)J recombination Junctional diversity Immunoglobulin class switching MHC/HLA

Lymphocytes

Substances

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