B cell IL-7. Human B cell lines constitutively secrete IL-7 and express IL-7 receptors.
IL-7 was originally reported as a cytokine produced by stromal cells which supports pre-B cell proliferation in vitro. To determine whether human B cells secrete IL-7 and express IL-7R we studied a wide panel of B cell lines (CLS). In Northern blot analysis we detected 2.4 kb IL-7 mRNA and by quantitative PCR we demonstrated IL-7 expression in 5 of 6 B CLS derived from patients with AIDS-associated Burkitt's lymphoma (AABCL), 3 of 3 CLS derived from patients with American Burkitt's lymphoma and 5 of 6 normal lymphoblastoid CLS. Only 1 of 5 African Burkitt's lymphoma CLS and 2 of 7 EBV- CLS expressed IL-7. A total of 484-bp amplicons was cloned and sequenced and found to correspond to the original IL-7 sequence. Constitutive IL-7 secretion was detected in 5 of 6 AABCL and in 6 of 7 normal lymphoblastoid CLS but in none of the 7 EBV- CLS. IL-7R expression was demonstrated in 8 of 26 CLS, none of which secreted IL-7. Our data suggest that 1) IL-7 mRNA is expressed in malignant B cell phenotypes, which correspond to a narrow window in the B cell differentiation pathway (pre-B, early B, intermediate B), as well as in normal lymphoblastoid B CLS. 2) IL-7 mRNA is expressed in both EBV+ and EBV- CLS, but only the EBV+ CLS secrete IL-7. 3) B cells activated by both EBV and HIV-1 (AABCL) secrete the greatest amount of IL-7. 4) IL-7 autocrine loops are not evident since IL-7R were detected on on CLS, which do not secrete IL-7. Our data provide the first direct evidence of IL-7 secretion by human cells and it is yet to be determined whether IL-7 is secreted by other cell types.
Benjamin
D
D
Division of Hematology and Oncology, Arthur G. James Cancer Hospital, Columbus, OH.
Sharma
V
V
Knobloch
T J
TJ
Armitage
R J
RJ
Dayton
M A
MA
Goodwin
R G
RG
D001402:B-Lymphocytes / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D006801:Humans; D015851:Interleukin-7 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D018123:Receptors, Interleukin / Q000032:analysis*; D020395:Receptors, Interleukin-7
D015851:Interleukin-7; D012333:RNA, Messenger; D018123:Receptors, Interleukin; D020395:Receptors, Interleukin-7