CD46 acts as a cofactor for complement factor I, a serine protease, which protects autologous cells against complement-mediated injury by cleaving C3b and C4b deposited on host tissue. It may be involved in the fusion of the spermatozoa with the oocyte during fertilization. CD46 acts as a co-stimulatory factor for T-cells, which induces the differentiation of CD4 into T-regulatory 1 cells. T-regulatory 1 cells suppress immune responses by secreting interleukin-10, and therefore are thought to prevent autoimmunity. A number of viral and bacterial pathogens seem to exploit this property and directly induce an immunosuppressive phenotype in T-cells by binding to CD46.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.