Entamoeba histolytica HM1 supported the activation of human alternative and classical complement pathways in the absence of ameba-reactive antibodies. Nonimmune serum depleted of C1q and factor D (NHS s C1q + D) and reconstituted with C1q was able to specifically deposit C3b onto trophozoites and produce lysis. This activity was not modified by the absorption of serum on E. histolytica. Serum d...

Removal of cells dying by apoptosis is essential to normal development, maintenance of tissue homeostasis, and resolution of inflammation. Surfactant protein A (SP-A) and surfactant protein D (SP-D) are high abundance pulmonary collectins recently implicated in apoptotic cell clearance in vitro. Other collectins, such as mannose-binding lectin and the collectin-like C1q, have been shown to bind...

Recent evidence suggests that the pathophysiology of neurodegenerative and inflammatory neurological diseases has a neuroimmunological component involving complement, an innate humoral immune defense system. The present study demonstrates the effects of experimentally induced global ischemia on the biosynthesis of C1q, the recognition subcomponent of the classical complement activation pathway,...

Activation of the complement system promotes the removal of pathogens and tissue damage products from the brain and may also be involved in neuronal cell death in neurodegenerative diseases. Here, we analyzed the expression of C1q, the initial recognition subcomponent of the classic complement cascade, in the substantia nigra pars compacta (SNc) in Parkinson disease (PD) and control cases using...

Two individual globular head regions (ghA and ghB) of the heterotrimeric C1q molecule (containing A, B, and C chains) were expressed in a bacterial expression system using a coproduction with the bacterial chaperone GroESL. The purified proteins were soluble and monomeric, as shown by gel-filtration analysis. No association into homotrimers was seen, which indicates that the ability to form het...

Dendritic cells (DC) and complement are both important effectors in innate immunity, and also potent linkers between innate immunity and adaptive immunity. As key components of innate immunity, various bioactive complement components produced at the inflammatory sites have been found to be able to regulate functions of DC. It is well known that migration of DC to the peripheral inflammatory sit...

The immunoglobulin G binding site in the globular regions of human complement subcomponent C1q has been investigated by chemical modification of histidine residues with diethylpyrocarbonate and arginine residues with phenylglyoxal and cyclohexane-1,2-dione (CHD). Only the modification of arginine residues with CHD fulfills the requirements of a specific modification without unwanted side reacti...

The first step in the activation of the classical pathway of the complement system by immune complexes involves the binding of the six globular heads of C1q to the Fc regions of IgG or IgM. The globular heads of C1q are located C-terminal to the six triple-helical stalks present in the molecule; each head is considered to be composed of the C-terminal halves (3x136 residues) of one A-, one B- a...