About IgM
Immunoglobulins (Ig) are the antigen recognition molecules of B cells. An Ig molecule is made up of 2 identical heavy chains and 2 identical light chains (see MIM 147200) joined by disulfide bonds so that each heavy chain is linked to a light chain and the 2 heavy chains are linked together. Each Ig heavy chain has an N-terminal variable (V) region containing the antigen-binding site and a C-terminal constant (C) region, encoded by an individual C region gene, that determines the isotype of the antibody and provides effector or signaling functions. The heavy chain V region is encoded by 1 each of 3 types of genes: V genes (see MIM 147070), joining (J) genes (see MIM 147010), and diversity (D) genes (see MIM 146910). The C region genes are clustered downstream of the V region genes within the heavy chain locus on chromosome 14. The IGHM gene encodes the C region of the mu heavy chain, which defines the IgM isotype. Naive B cells express the transmembrane forms of IgM and IgD (see IGHD; MIM 1471770) on their surface. During an antibody response, activated B cells can switch to the expression of individual downstream heavy chain C region genes by a process of somatic recombination known as isotype switching. In addition, secreted Ig forms that act as antibodies can be produced by alternative RNA processing of the heavy chain C region sequences. Although the membrane forms of all Ig isotypes are monomeric, secreted IgM forms pentamers, and occasionally hexamers, in plasma (summary by Janeway et al., 2005).[supplied by OMIM, Aug 2010]

About PerCP-Cy5.5
PerCP-Cyanine® 5.5 (PerCP-Cy5.5) is a red-emitting tandem fluorophore that was originally designed to make the PerCP fluorophore more stable and increase signal intensity. The donor molecule, PerCP can be excited by the 488-nm blue laser and and transfers energy to the acceptor molecule, Cy5.5, which emitts light that can be captured with a 695/40 nm bandpass filter. PerCP-Cy5.5 has an excitation peak at 482 nm and an emission peak at 695 nm. There are superior alternatives to PerCP and PerCP-Cy5.5 including BB700, NovaFluor Blue 690 or PerCP-eFluor™ 710