Complement C1q A Chain (C1qa) is a subunit of C1q. C1q is composed of 6 polypeptide chains each of C1qa, C1qb, and C1qc. C1q is a component of the classical complement pathway, and thereby plays an important role in the immune response. Each C1q subunit contains an N-terminal collagen-like region and a C-terminal C1q globular domain. The presence of receptors for C1q on effector cells modulates its activity, which may be antibody-dependent or independent. Macrophages are the primary source of C1q, while anti-inflammatory drugs as well as cytokines differentially regulate expression of the mRNA as well as the protein. C1q deficiency is associated with lupus erythematosus and glomerulonephritis. Primary antibodies are available purified, or with a selection of fluorescent CF® Dyes and other labels. CF® Dyes offer exceptional brightness and photostability. Note: Conjugates of blue fluorescent dyes like CF®405S and CF®405M are not recommended for detecting low abundance targets, because blue dyes have lower fluorescence and can give higher non-specific background than other dye colors.