Question

Design a technique that would let you use a complement to selectively remove one cell type from a cell mixture. BE SPECIFIC on what I need to know about the cell to make this work.

Answer 1

complement system consist of glycoprotiens and protein system that bind specifically to antigen of foreign cell or antigen antibody complex. for example if we talk about bacteria as pathogen the lipollysaccharide present over it surface is the target of C1 Complex, specifically C1q can also to antigen antibody complex. This further activate cascade ultimately leading to membrane attack complex formation resulting the pore formation in pathogenic cell and its osmotic lysis.

The alternative complement pathway is able to distinguish self from non-self on the basis of the surface expression of complement regulatory proteins. Host cells don't accumulate cell surface C3b (and the proteolytic fragment of C3b called iC3b) because this is prevented by the complement regulatory proteins, while foreign cells, pathogens and abnormal surfaces may be heavily decorated with C3b and iC3b. Accordingly, the alternative complement pathway is one element of innate immunity

MANNOSE BINDING LECTIN (MBL)

MBL binds to a range of sugars including N-acetyl-D-glucosamine, mannose, N-acetyl-mannosamine, fucose and glucose. This permits the protein to interact with a wide selection of viruses, bacteria, yeasts, fungi and protozoa decorated with such sugars. Unlike the other collectins, MBL bound to microbial surfaces is able to activate the complement system in an antibody and C1-independent manner. This activation is mediated by complexes of MBL with a serine protease called MBL-associated serine protease 2 (MASP-2), which specifically cleaves C4 and C2 to create a C3 convertase enzyme. MBL may also interact directly with cell surface receptors and thereby promote opsonophagocytosis by a complement-independent pathway. It has been suggested that MBL plays an important role in the first hours/days of any primary immune response to a sugar decorated pathogen.

The complement protein binding to pathogen or foreign cell could be used in separation from other cell population through various technique including FACS ( Fluorescence-activated cell sorting ) based on size.