Both antibody-dependent and independent complement pathway converge on which complement component?

Complement is a collective term that describes a system of about 20 proteins, many of which are enzyme precursors. All these are present normally among the plasma proteins in the blood as well as among the proteins that leak out of the capillaries into the tissues. They are usually inactive i.e. enzyme precursors They are activated by two pathways i. Classic pathway ii. Alternate pathway Classic pathway - The classical pathway is initiated by an antigen-antibody reaction. Alternative pathway Alternative pathway complement activation does not require the interaction of complement with an antigen /antibody complex. Rather a bacterial lipopolysaccharide (LPS, endotoxin) and other general bacterial substances (also immunoglobulin A aggregates) can activate complement. In both the classical and alternative pathways a key outcome is the conversion of the C3 component of complement into C3a and C3b proteins. Both the pathways follow different course only up to the activation of C3. Activation or splicing of the C3 is the convergence point of both the pathways, after which both the pathways follow the same course.