Expression of Interleukin 5 by the CD4+CD45RO+Subset of Human T Cells

The expression of IL5 by CD4(+)D45RA(+), CD4(+)CD45R0(+) and CD3(+)CD8(+) subsets of human peripheral blood mononuclear cells was assessed. Interleukin 5 expression was detected by RNA extraction, reverse transcription and polymerase chain reaction. Populations of highly purified cells were obtained by a protocol of sequential plastic adherence, magnetic bead separation and flow cytometric cell sorting. IL5 was clearly expressed in the CD4(+)CD45R0(+) subset from 3 to 48 hr after activation. The CD4(+)CD45RA(+) and CD3(+)CD8(+) subsets expressed very much less IL5. By contrast, IL2 expression was readily detected in all sorted populations. Thus, in activated CD4(+) cells, IL5 was predominantly expressed in the CD4(+)CD45R0(+) subset, a pattern of expression corresponding to that reported for a number of other cytokines, and differing from that of IL2.