Secretion of thioredoxin after in vitro activation of human B cells.
The redox-active enzyme thioredoxin (Trx) is secreted by various virus-transformed cell lines of B- and T-cell origin and has been considered to play an autoregulatory role as a cofactor during cellular growth processes. We show in this paper that exposure of B lymphocytes from normal, healthy donors and B cells from B-type chronic lymphocytic leukemia (B-CLL) to Staphylococcus aureus Cowan I (SAC) induced expression of Trx mRNA. By combining SAC, or the phorbol ester TPA, with IL-2 and the conditioned medium of a T-cell hybridoma (BSF-MP6), we could strongly enhance the Trx expression. After [35S]methionine labeling of stimulated B-CLL cells in vitro, Trx was immunoprecipitated both from cell extracts and from the medium with antibodies against human placenta Trx. Secretion of newly synthesized Trx was also confirmed by a quantitative radioimmunoassay for human Trx. During 24 h cultivation experiments, treatment with SAC induced a 5-fold increase of the Trx content of normal B lymphocytes as well as in B-CLL cells. Approximately two-thirds of the total amount of the enzyme was released into the medium.
Ericson
M L
ML
Department of Biochemistry, Karolinska Institutet, Stockholm, Sweden.
Hörling
J
J
Wendel-Hansen
V
V
Holmgren
A
A
Rosén
A
A
D001402:B-Lymphocytes / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D016193:G1 Phase; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry; D008213:Lymphocyte Activation; D014066:Palatine Tonsil; D012333:RNA, Messenger / Q000096:biosynthesis; D011956:Receptors, Cell Surface / Q000187:drug effects; D013211:Staphylococcus aureus; D013879:Thioredoxins / Q000378:metabolism*
D007136:Immunoglobulins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D013879:Thioredoxins