Heterogeneity in P-glycoprotein (multidrug resistance) activity among murine peripheral T cells: correlation with surface phenotype and effector function.
P-glycoprotein (P-gly) is the transmembrane efflux pump responsible for multidrug resistance in tumor cells. Functional P-gly activity can be conveniently assessed microfluorometrically using the fluorescent dye rhodamine 123 (Rh123), which is an artificial substrate for the P-gly transporter. Here we assess P-gly activity in subsets of mouse peripheral T lymphocytes using the Rh123 efflux assay. Our data indicate that virtually all CD8+ cells extrude Rh123 efficiently, whereas only a subset of CD4+ cells exhibit P-gly activity. Correlation of P-gly activity in CD4+ cells with the expression of a panel of surface markers revealed that cells bearing an "activated/memory" phenotype (CD45RB-, CD44hi, CD62L-, CD25+, CD69+) were exclusively found in the fraction that can extrude Rh123. In contrast "naive" phenotype CD4+ cells (CD45RB+, CD44lo, CD62L+, CD25-, CD69-) could be further subdivided into two major subsets based on P-gly activity. In functional studies of sorted cell populations the Rh123-extruding subset of "naive" CD4+ cells proliferated more strongly and secreted higher levels of interleukin (IL)-2 than its Rh123-retaining counterpart when activated by a variety of polyclonal stimuli. Furthermore, this subset produced detectable levels of interferon (IFN)-gamma upon stimulation but no IL-4 or IL-10. As expected, the Rh123-retaining "naive" subset produced only IL-2 after stimulation, whereas the "memory" subset produced IFN-gamma, IL-4 and IL-10 in addition to low levels of IL-2. Collectively, our data indicate that P-gly activity is a novel parameter that can be used to distinguish a subset of "preactivated" CD4+ cells that would be considered as naive on the basis of their surface phenotype.
Bommhardt
U
U
Ludwig Institute for Cancer Research, University of Lausanne, Epalinges, Switzerland.
Cerottini
J C
JC
MacDonald
H R
HR
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000367:Age Factors; D000818:Animals; D001483:Base Sequence; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism*; D016207:Cytokines / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D016130:Immunophenotyping; D017493:Leukocyte Common Antigens / Q000378:metabolism; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D020112:Rhodamine 123; D012235:Rhodamines / Q000378:metabolism; D016176:T-Lymphocyte Subsets / Q000378:metabolism*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D016207:Cytokines; D017931:DNA Primers; D012235:Rhodamines; D020112:Rhodamine 123; D017493:Leukocyte Common Antigens