MultiDots consist of several quantum dots within a patented PEG polymer coating. The pegylated fluorescent nanoparticles have very tight size distribution and the amine functional groups on the surface allows conjugation of proteins to label cells of interest. MultiDots with a tighter emission spectrum than current fluorescent reagents, reduces spectral overlap, increases assay sensitivity and eliminates complex spectral compensation. The SK1 antibody conjugated this MultiDot is specific for the 32-34 kDa alpha chain of human CD8, known as CD8a or CD8 alpha. CD8a can form a homodimer (CD8 alpha-alpha), but is more commonly expressed as a heterodimer with a second chain known as CD8b or CD8 beta. CD8 acts as a co-receptor for antigen recognition and subsequent T cell activation that is initiated upon binding of the T cell receptor (TCR) to antigen-bearing MHC Class I molecules.