Interleukin-7R alpha mRNA expression increases as stem cells differentiate into T and B lymphocyte progenitors.
The gamma common (gamma c) chain is a partner in several interleukin receptor complexes, including the interleukin-2 receptor (IL-2R), IL-4R, and IL-7R. Mutations in the gamma c gene are associated with X-linked severe combined immunodeficiency (SCID). Using reverse transcriptase-PCR, we examined the level of mRNA-encoding gamma c and its partners in mouse pluripotent hematopoietic stem cells (PHSCs), which repopulate both bone marrow and thymus. We also assayed developing lymphocytes to define which, if any, IL-R complexes are expressed at the earliest stage of T and B lymphocyte maturation. RNA extracted from bone marrow-derived PHSCs did not contain detectable levels of mRNA-encoding IL-7R alpha. However, the most primitive (CD4- CD8-) T cells from the thymus and the most primitive (c-kit+ B220+) B cells from bone marrow contained high levels of IL-7R alpha mRNA. There were no detectable differences between PHSCs and primitive or more mature T and B cells for expression of gamma c mRNA. We conclude that the onset of IL-7R formation occurs at the earliest stage of differentiation of T and B lymphocytes. Our findings are consistent with the hypothesis that the absence of an intact IL-7R (IL-7R alpha and gamma c) may be a critical loss that interrupts lymphopoiesis.
Orlic
D
D
Hematopoiesis Section, NHGRI, NIH, Bethesda, MD 20892-4442, USA.
Girard
L J
LJ
Lee
D
D
Anderson
S M
SM
Puck
J M
JM
Bodine
D M
DM
D000818:Animals; D015703:Antigens, CD / Q000235:genetics*; D001402:B-Lymphocytes / Q000502:physiology*; D001854:Bone Marrow Cells; D002454:Cell Differentiation; D002469:Cell Separation; D005260:Female; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D017493:Leukocyte Common Antigens / Q000032:analysis; D051379:Mice; D008810:Mice, Inbred C57BL; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis; D012333:RNA, Messenger / Q000235:genetics; D018121:Receptors, Cytokine / Q000235:genetics; D018123:Receptors, Interleukin / Q000235:genetics*; D020395:Receptors, Interleukin-7; D013601:T-Lymphocytes / Q000502:physiology*
D015703:Antigens, CD; D012333:RNA, Messenger; D018121:Receptors, Cytokine; D018123:Receptors, Interleukin; D020395:Receptors, Interleukin-7; D019009:Proto-Oncogene Proteins c-kit; D017493:Leukocyte Common Antigens