"CD3low" human thymocyte populations can readily be triggered via the CD2 and/or CD28 activation pathways whereas the CD3 pathway remains nonfunctional.
We have investigated the role of the CD2 and the CD28 Ag-independent pathways of activation on CD3low thymocytes. We previously showed that anti-CD28 mAb synergized with anti-CD2 mAb directed against epitopes T11.1 and T11.2, in the activation of purified resting T cells or unseparated thymocytes. Proliferation induced via CD2 plus CD28 was mediated via an IL-2-dependent pathway and was not affected by prior modulation of the CD3-TCR complex. Here, we show that a subset of CD3low thymocytes, although unresponsive to CD3 activation, can be activated to proliferate through the CD2 or the CD28 pathways, in the presence of exogenous IL-2. The mitogenic combination of mAb to CD2 and CD28 induces a proliferation of thymocytes which, in absence of exogenous lymphokines, is restricted to the more mature intrathymic subpopulation, CD1a-. However, CD3low thymocytes can also be triggered through the CD2 plus CD28 activation pathways but require at least addition of exogenous IL-2 to proliferate. This study demonstrates that a fraction of immature CD3low thymocytes possesses functional CD2 and CD28 surface molecules at a time when CD3 is not yet functional.
Pierres
A
A
Unité de Cancérologie et Thérapeutique Experimentale, U. 119 Inserm, Marseille, France.
Cerdan
C
C
Lopez
M
M
Mawas
C
C
Olive
D
D
D000367:Age Factors; D015703:Antigens, CD / Q000502:physiology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology*; D018801:CD2 Antigens; D018106:CD28 Antigens; D017252:CD3 Complex; D002455:Cell Division; D002469:Cell Separation; D005455:Fluorescent Antibody Technique; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology; D007378:Interleukins / Q000494:pharmacology; D008213:Lymphocyte Activation; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D011971:Receptors, Immunologic / Q000502:physiology*; D013601:T-Lymphocytes / Q000502:physiology*; D013950:Thymus Gland / Q000166:cytology
D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018801:CD2 Antigens; D018106:CD28 Antigens; D017252:CD3 Complex; D007376:Interleukin-2; D007378:Interleukins; D011948:Receptors, Antigen, T-Cell; D011971:Receptors, Immunologic