Interleukin 2 receptor regulation and IL-2 function in the human infant.
IL-2 receptor is expressed at low levels on adult blood lymphocytes, and at lower levels on cord blood cells. IL-2 receptor alpha and beta chain expression increases gradually from 0-18 months of age. The level of soluble CD25 (IL-2 receptor alpha chain) has been reported to be elevated in cord blood. Quantitative RT-PCR showed that adult cells express 10 times as much CD25 mRNA as cord cells. Cord plasma showed only a marginal ability to strip CD25 from the membrane. To assess the functional consequences of low IL-2 receptor expression, cord and adult cells were activated in vitro. The response was stimulus-dependent, but cord cells upregulated CD25 readily. Cord and adult cells proliferated in an IL-2-dependent assay to a similar extent. Infants suffering acute infection showed marginally higher levels of membrane CD25 expression than infants without overt infection. Thus neonatal and infant lymphocytes express lower levels of IL-2 receptors than adult cells, reflecting lower mRNA concentrations at least for CD25; they are able to up-regulate receptors in response to in vitro stimulation and are able to respond in vitro to IL-2-dependent stimulation; however in vivo there may be a dampening down of the IL-2 system in infancy.
Child Health Research Institute, Adelaide, Australia. hzola@medicine.adelaide.edu.au
H
H
Zola
J
J
Ridings
S
S
Elliott
S
S
Nobbs
H
H
Weedon
L
L
Wheatland
R
R
Haslam
D
D
Roberton
P J
PJ
Macardle
D000328:Adult; D000367:Age Factors; D003141:Communicable Diseases / Q000276:immunology; D015536:Down-Regulation; D005312:Fetal Blood / Q000276:immunology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007239:Infections / Q000276:immunology; D007376:Interleukin-2 / Q000276:immunology*; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008213:Lymphocyte Activation; D012333:RNA, Messenger / Q000032:analysis; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis* / Q000235:genetics; D015854:Up-Regulation
D007376:Interleukin-2; D012333:RNA, Messenger; D015375:Receptors, Interleukin-2