Detection of lymphocyte subsets using three-color/single-laser flow cytometry and the fluorescent dye peridinin chlorophyll-alpha protein.

The fluorescent dye, Peridinin chlorophyll A protein (PerCP) derived from dinoflagellate organisms (Glenodinium sp.) can be excited by a 488 nm laser and emits light with a large Stokes shift and no major spectral overlap with commonly used chromophores such as fluorescein isothiocyanate (FITC) and R-phycoerythrin (PE). PerCP was conjugated directly to various mouse monoclonal antibodies (mAb) specific for human leukocyte markers or to avidin for use with biotinylated-mAb, and used to perform three color single-laser flow cytometry. The efficacy of this method was demonstrated by analyzing the heterogeneity of thymus T lineage subsets and B lymphocyte subsets in blood. CD4-CD8-, CD4+CD8+ and CD4+CD8- or CD4-CD8+ subsets differ in their expression of cell-cell interaction markers including CD18, CD28, CD44 and Leu 8, and activation/subset markers CD45RO, CD45RA and CD26. Some CD5+ peripheral blood B cells, unlike CD5-B cells, expressed CD45RO or high levels of CD54 (ICAM-1) suggesting the CD5+ B cell population contains activated lymphocytes. The availability of such an accessible method for three color analysis will make it possible to do routine three color monitoring of immunologic diseases such as AIDS, and autoimmune or periodontal diseases.