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 HIB19 antibody conjugated to this MultiDot reacts with CD19, a 95 kDa type 1 transmembrane glycoprotein expressed on the surface of B cells throughout all stages of development, from early pre-B cells to plasma cells. CD19 can also be found on follicular dendritic cells. CD19 also functions as a co-receptor with CD21 and CD81 for the B cell receptor and is involved in B cell activation and differentiation.