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Queensland Institute of Medical Research,
Joint Transplantation Biology Program, University of Queensland, and
Cooperative Research Centre for Vaccine Technology, Brisbane, Queensland, Australia
The signals that trigger IL-4-independent IL-4 synthesis by
conventional CD4+ T cells are not yet defined. In this
study, we show that coactivation with anti-CD4 mAb can stimulate
single naive CD4+ T cells to form IL-4-producing clones in
the absence of APC and exogenous IL-4, independently of effects on
proliferation. When single CD4+ lymph node cells from
C57BL/6 mice were cultured with immobilized anti-CD3
mAb and
IL-2, 6585% formed clones over 1214 days. Coimmobilization of mAb
to CD4, CD11a, and/or CD28 increased the size of these clones but each
exerted different effects on their cytokine profiles. Most clones
produced IFN-
and/or IL-3 regardless of the coactivating mAb.
However, whereas 06% of clones obtained with mAb to CD11a or CD28
produced IL-4, 1040% of those coactivated with anti-CD4 mAb were
IL-4 producers. A similar response was observed among CD4+
cells from BALB/c mice. Most IL-4-producing clones were derived from
CD4+ cells of naive (CD44low or
CD62Lhigh) phenotype and the great majority coproduced
IFN-
and IL-3. The effect of anti-CD4 mAb on IL-4 synthesis
could be dissociated from effects on clone size since anti-CD4 and
anti-CD11a mAb stimulated formation of clones of similar size which
differed markedly in IL-4 production. Engagement of CD3 and CD4 in the
presence of IL-2 is therefore sufficient to induce a substantial
proportion of naive CD4+ T cells to form IL-4-producing
clones in the absence of other exogenous signals, including IL-4
itself.
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