Proliferation of murine T lymphocytes in blood, lymph nodes, and spleen was
studied in four in vivo stimulation systems, using BrdU pulse-labeling of
DNA-synthesizing cells. The T cell response to the superantigen Staphylococ
cus enterotoxin B (SEB) was studied in detail, V beta 8(+) T cells showed a
peak of DNA synthesis 16-24 h after SEE injection, and the percentage of B
rdU(+) CD4 and CDS T cells was higher in blood than in lymph nodes and sple
en. DNA synthesis was preceded by massive migration of V beta 6(+) cells fr
om blood to lymphoid organs, in which the earl! activation marker CD69 was
first up-regulated, SEB-nonspecific V beta 6(+) cells showed minimal stimul
ation but, when cycling, also expressed a high level of CD69, The other sys
tems studied were injection of the IFN-gamma inducer polyinosinic:polycytid
ylic acid, infection by the BM5 variants of murine leukemia virus (the caus
ative agent of murine AIDS), and T cell expansion after transfer of normal
bone marrow and lymph node cells into recombinase-activating gene-2-deficie
nt mice, Ln each case, a peak of T cell proliferation was observed in blood
. These data demonstrate the extensive redistribution of cycling T cells in
the first few hours after activation. Kinetic studies of blood lymphocyte
status appear crucial for understanding primary immune responses because cy
cling and redistributing T lymphocytes are enriched in the circulating comp
artment.