Antigen-independent pathways of T-cell activation are functional in human immature thymocytes

Alessandro Poggi, Maria Raffaella Zocchi

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The signal requirements for proliferation of CD1+CD3- immature thymocytes have been studied in order to define whether this immature cell population could function despite the lack of the CD3/T-cell receptor complex. We found that CD1+CD3- cells proliferate upon stimulation with anti-CD28 monoclonal antibody as well as with a pair of anti-CD2 monoclonal antibodies in the presence of low doses (0.5 ng/ml) of phorbol-13-myristate-12-acetate and/or recombinant interleukin-2. A minor fraction of CD3+ cells (15%-20%) was also present in the proliferating cell population originating from CD1+CD3- thymocytes stimulated with phorbol-13-myristate-12-acetate and recombinant interleukin-2, either in the presence or in the absence of specific monoclonal antibodies. We further observed that the anti-CD3 monoclonal antibody did not induce the proliferation of CD1+CD3- cells, as expected, and efficiently triggered unfractionated or CD1+CD3+ thymocytes only if exogeneous recombinant interleukin-2 was provided. Unexpectedly, we noted that highly purified (>99%), CD1+CD3- immature thymocytes could mobilize calcium via CD3, besides CD2 and CD28 surface molecules, suggesting that a minor undetectable fraction (+ cells was still present in the purified CD3- population. Nevertheless, the preferential expansion of CD3-CD8+ cells (about one-third of proliferating cells) after triggering via CD28, and to a lesser extent via CD2, support the notion that the alternative pathways of T-cell activation are actually functional in CD1+CD3- immature thymocytes.

Original languageEnglish
Pages (from-to)304-309
Number of pages6
JournalInternational Journal of Clinical & Laboratory Research
Issue number2-4
Publication statusPublished - Jun 1992


  • CD2 activation pathway
  • CD28 activation pathway
  • CD3 thymocytes
  • T-cell activation
  • Thymocyte activation

ASJC Scopus subject areas

  • Clinical Biochemistry


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